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2002 E39 ASC BRAKE ABS lights on => Diagnostic Procedure & Parts Location

1M views 1K replies 213 participants last post by  MeisterSchnitzelBrau 
#1 ·
Oh my. My 2002 BMW E39 has these three lights lit on my instrument cluster:
- Triangle (is it ASC or DSC?)
- Brake
- ABS

I see there are lots of threads on this so I'm reading through them, but, they all seem to know already if it's ASC or DSC they're dealing with.

Am I dealing with ASC or DSC?

ASC (automatic stability control) apparently senses 4-wheel differential speeds during cornering and cuts the engine power via a second throttle butterfly valve to help keep you from oversteering and spinning out in wet/snowy/unfavorable conditions. It may also apply the rear brakes lightly in some situations. It apparently doesn't touch the suspension at all. It has been described as ABS in reverse. Reputedly, while ABS controls the braking force at all four wheels, ASC + T controls the power delivery of the engine, and the way the rear differential distributes torque between the two back wheels only.

DSC (dynamic stability control) in contrast, is apparently a suspension-control system which goes beyond Automatic Stability Control + Traction by monitoring steering wheel movement, vehicle speed, transverse acceleration and yaw to register imminent instability when cornering. DSC then intervenes via the engine management system reducing drive torque and activating wheel brakes when necessary to keep the vehicle stable.

Having said all that, how do I know if my 2002 E39 has ASC or DSC?
(I think it's ASC but I need to know before beginning my troubleshooting.)


 

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#3 ·
Would constant battery disconnects cause the indicators to light?

Your 525 is 2002 which has the DSC.
Thanks.

It's weird, but, for the past three days, sometimes the three triangle/ABS/Brake warning indicators are on, other times only the two ABS/Brake indicators are on, and other times none are on (see photos below).

I wonder if this problem is related to the fact I've been constantly disconnecting my battery to reset the DICE iPod interface.

 

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#4 ·
Have you tried the warning light reset procedure?

Normally when you've got all those lights lit up, it's a problem with the DSC module.
 
#7 ·
Where is the canonical DSC/ABS CEL brake troubleshooting thread

Have you tried the warning light reset procedure?
I'm still in the "research" stage... trying to find the canonical DSC/ABS CEL brake troubleshooting thread.

In summary, after reading some of the many threads...

Is this the DSC/ABS/Brake warning indicator diagnostic procedure?
- Determine what is being displayed to me (I'm in this stage)
- Understand how the system works (sensors tied to modules tied to lamps)
- Locate the sensors (4?) and associated control modules (2?)
- Read the ABS CEL OBDII error codes with the Carsoft 6.5.1 hardware
- Reset the ASC/ABS/Brake warning indicators & test the car
... If the problem re-occurs ...
- Determine if the problem is in the sensors, and if so, which one(s)
- Determine if the problem is in the modules, and, if so which one(s)
- If modules, decide whether to fix the module & reprogram or buy new
- Install new (or fixed) sensors or modules & test the system again

Is that the basic diagnostic procedure for DSC/ASC/ABS CEL warnings?
 
#6 ·
Same here. They'd go off sometimes, and then back on again a while later, but I'm pretty sure it was always all 3 lights. Of course, on my car I had the extra bonus that whenever I'd turn on the headlights, or the stereo up really loud, I'd get the transmission going into failsafe mode. I basically couldn't drive the car at night. That was related to the ABS module, as well (not enough eletrical current at the transmission control module).

If it is your ABS module, I'd recommend Module Master. They're also on Ebay under Circuit Solutions. They fixed mine and I think it cost me $325 including return shipping. They also provide a 5 year warranty on the repair.
 
#8 ·
You may want to consider BBA Remanufacturing. They could not fix my unit, but they will honor the warranty and they have great customer service. My indy now is saying that the problem is the "precharge unit," whatever that is. I'm undecided about fixing it--he quoted me $850. My ABS works fine and only my DSC light remains lit.
 
#10 · (Edited)
Even after a full-fledged DICE battery reset procedure, I still have the DSC ABS BRAKE lights going on after a while of driving.

So, I'm gonna Carsoft the thing this weekend and let you know the codes so you can help me better.

One problem (a good one, I guess) is there is a lot of information about this problem scattered about - but I haven't found the one jewel of a thread (maybe we can make this one that so others benefit from our efforts).

Donna
 

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#11 · (Edited)
Short answer: your module's shot and/or you need new sensor(s).

Based on the fact that it's intermittent and you've been fooling with the battery (I'm assuming the DICE install doesn't require you to get into you wheel wells or the steering column), it's the module. If you want to be sure, get the BMW STEALER (i.e. the guy with the expensive computer) to read the codes. Few aftermarket readers can.

What's the display going on about? Detached? Is that the DICE? Also, bloody cold in NorCal apparently!

Edit: It's possible to fix the module yourself, in some cases, apparently. Volvo owners have been doing it for a while. If you're handy with a soldering iron and have a vise and Dremel or hacksaw, you could try fixing it yourself. However, this assumes that you have chip creep with fully functional chips, rather than blown chips and solder in good shape.
 
#12 · (Edited)
Short answer: your module's shot and/or you need new sensor(s).
I know. I know. I hope to figure out the diagnosis procedure and document it in this thread (if it's not fully documented elsewhere).

My first task is to find a picture of the module and sensors (I think the sensor picture will be easy ... I might even already have one from my brake job - but where is the ABS module location in the engine bay?

get the BMW STEALER (i.e. the guy with the expensive computer) to read the codes. Few aftermarket readers can.
Do you think Carsoft 6.5.1 can read these codes correctly?

Detached? Is that the DICE?
Yes. Detached means the iPod isn't hooked up to the DICE at that moment I snapped the photograph. Otherwise the song name and artist would be displayed on the instrument cluster.

bloody cold in NorCal apparently!
Yea. It was "freezing" here in San Jose this morning. 60 degrees F at 6am at 60 miles per hour when I snapped that shot of my display. Brrrrrrr.... :)

you could try fixing it yourself.
It may come to that. I don't mind purchasing whatever tools I need; it's what I do to get to the bottom of things.

 
#13 · (Edited)
What is the mysterious BMW OEM "repair kit" for the ASC control unit?

After a week now, I can report that I don't have the symptoms of intermittent speedometer but I do have all three DSC or ASC, ABS, & BRAKE lights lit on my instrument cluster after a period of time after I start the 2002 E39, so it's looking like either the 4 wheel-speed sensors or the ABS module itself.

If it's the ABS module itself, it looks like REALOEM lists it as:
E39 525i ASC hydro unit/control unit/support
01 Hydro unit ASC 34516756341 $2,003.22
02 Repair kit, control unit ASC 34526756343

Do you know what this BMW OEM "repair kit" is? It's not mentioned in the ABS fix DIY which says it can be repaired by these two companies:
1. Module Masters
2. BBA Remanufacturing

So, I ask, what is this BMW OEM repair kit anyway?

Also, do we have self-repair instructions handy (the bimmerfest search button is broken - it constantly reports "connection to three.performanceix.com:3312 failed".

 

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#14 ·
Nobody buys the thing called "Hydro Unit ASC" it seems

Since nobody on Bimmerfest knew the answer, I called the local dealership who said that nobody ever buys the #1 thing called "Hydro unit, ASC"; he said everyone buys the #2 thing called "repair kit, control unit asc".

Prices out the door at the California dealership for parts are:
- #1 Hydro unit, ASC ===> $2,775 + $277 (~10% tax) = $3,052
- #2 Repair kit, control unit ASC ===> $1,120 + $112 (~10% tax) = $1,232
- 2x sensors front ===> $134 x 2 = $268 + $27 (~10% tax) = $295
- 2x sensors rear ===> $201 x 2 = = $402 + $40 (~10% tax) = $442

Is this the sum total of "suspect" parts?

Or is there an "ABS CONTROL UNIT" that we also need to look at?
 
#15 ·
Does anyone have a set of PICTURES of ABS parts in an E39?

- #1 Hydro unit, ASC ===> $2,775 + $277 (~10% tax) = $3,052
- #2 Repair kit, control unit ASC ===> $1,120 + $112 (~10% tax) = $1,232
- 2x sensors front ===> $134 x 2 = $268 + $27 (~10% tax) = $295
- 2x sensors rear ===> $201 x 2 = = $402 + $40 (~10% tax) = $442
Does anyone have a set of PICTURES of each of these parts in an E39?
 
#18 · (Edited)
Does anyone have a set of PICTURES of each of these parts in an E39?
I might, tomorrow, if my mom lets me steal her camera and pull my wheels off. I believe QSilver7 may have some of the pics. The first attachment is the DSC connector in the car. The silver part is the hydro unit; the black part (also featured in the second image) is the module, which I believe to be the repair kit.

- #1 Hydro unit, ASC ===> $2,775 + $277 (~10% tax) = $3,052
That seems to be the hedgehog-like bit that the ASC control unit bolts on to; i.e. the milled aluminium part.
- #2 Repair kit, control unit ASC ===> $1,120 + $112 (~10% tax) = $1,232
Plastic bit that everyone sends in. The "module". As far as I can tell. Very expensive apparently; shouldn't be that much. If it comes to it, email Jared. :dunno:
- 2x sensors front ===> $134 x 2 = $268 + $27 (~10% tax) = $295
- 2x sensors rear ===> $201 x 2 = = $402 + $40 (~10% tax) = $442
You saw them when you did the brakes. BMW will probably charge an hr labour. A child could do it once the wheel is off. It's technical like an oil change :)

You have DSC. Not ASC. Don't mix them up! The ASC module is much more expensive than the DSC afaik. There's several major differences as well. The dealer should've pointed this out if you called about an '02.
 

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#17 · (Edited)
Hi Bluebee! I'm having the same issue on my 540it at 84k miles. I totally missed that you were having this issue.

http://www.bimmerfest.com/forums/showthread.php?t=363554&highlight=

Carsoft pointed out the right rear wheel sensor was bad. I reset the code, drove around a bit and it returned. So I first cleaned the wheel sensor:
  • Take off rear wheel
  • 3mm allen(?) to remove sensor retention screw
  • Pull sensor out of hub assembly, straight up. A little twisting back and forth helps
  • Clean with CRC electronic cleaner
  • Replace sensor back into hub assembly, snug tighten
  • Replace rear wheel, tighten to 88lbs.
Woo Woo! All lights went off. :roundel:

:( Next day, all lights return. Replaced wheel sensor, but to no avail. I've been suspecting the ABS module as the light will go out when the car has cooled down, only to return when the car is heated up again.

Spoke with Jared at EAC. He confirmed the type of failure and symptoms. Noted that the false Carsoft reading could happen if the ABS Module itself was bad and not able to report status correctly.

I ordered a replacement new ABS/DSC Bosch unit from EAC for $450. I wanted the swiftest fix, with the least hassle. (I'll offer mine up for sale as a repair core if someone is interested, PM me next week) Once I install it, I'll head over to an Indy who can code the VIN into it and activate the unit with their software tools. For installation, 4 Torx bolts and an electrical connector I'm told is the extent of the physical installation. I'll take pics and post a DIY as a few folks have similar questions.

I could have used the DSC today as it is raining pretty steady, but instead, will drive nice and calm today...

Good luck Donna with your troubleshooting! I know it will result in good info for us all as usual! :thumbup:
 
#19 · (Edited)
For installation, 4 Torx bolts and an electrical connector I'm told is the extent of the physical installation. I'll take pics and post a DIY as a few folks have similar questions.
Woo hoo! That's what I was hoping to find. I've been very busy lately (relationship and work issues galore) so I haven't even checked the Carsoft yet.

It's interesting that it didn't really help you (apparently because the ABS gave bad input about the probably-good sensor) - I'll report what my results are ... hopefully this weekend as I mope around all depressed!

 

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#30 ·
Is this the location of my E39 ABS computer control module?

I'm confused.

The thing that looks like the ABS computer is on the wrong side of the engine (it's on the passenger side, not on the drivers side).

Is THIS thing (see picture below) the ABS computer on my 2002 E39?
 

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#36 ·
#32 ·
Tamper dot came on

Hello all,
I replaced the LCM on my 97 E-39 sedan with one I picked up at a salvage yard. All of my lights are now working fine. The tamper dot came on as the replacement part was from another vehicle. My concern, is this tamper dot something I need to be concerned with as I'm about to hit the road for vacation about 1600 miles and is there danger of harm to other systems on my vehicle.
Took it to a indy shop to have it coded they came up with the fault code indicating the mismatch.
Help please!!!!!!1:mad:
 
#33 ·
the car on the right in the pics above must be a UK car or a mirror image :\***8230;..unless they flipped the washer tanks around too.

No harm will come to your car if you drive with the tamper dot, but it's going to be difficult to sell the car. The dot's there to prevent sale using false weights and measures. Preferably make a new thread if you have an unrelated question.
 
#34 ·
Yes, that's the module, there are 6 torx screws I believe.
Bluebee or anybody else; Do you happen to know how are the abs pulse generators supposed to read? I took both of my front ones off the wheel and they both go to infinity (open) when read, I tried different scales just in case I'm loosing my mind. I thought they were supposed to read something like 4 MOhm. If that's the case, then both left and right fronts are gone on my car. I also have the nice tro of amber lights...
 
#35 ·
I had success, but it likely cost me $105 for a module re-build that I didn't need. After getting the three lights of death, I just flipped a coin and sent the module off to ATE for a lifetime guarantee rebuild. They advised they would test it first, but rebuild it even if it checked "ok" as the heat will get it sooner or later. Got it back and the errors were still there. Did the "diode test" and 3 wheel sensors showed just fine and the front passenger was open-clearly bad. Replaced it for $65 from AutoHauz and all is good once again. Don't even need to clear the error. It clears itself.
 
#40 ·
""""Here is a link to so you can see the steering column in an exploded view. You'll be looking at part "9". There are 3 different sensors steering angle sensors listed. I picked up a new one from FCP Groton for 260 shipped (it is an OEM sensor)
http://www.realoem.com/bmw/showparts...00&hg=32&fg=30

I could not copy the file from TIS. Here is what the document states. It doesn't seem like much help unless you have a BMW diagnosis system at your disposal.

document number 61 31 996 Carry out steering angle sensor adjustment
IMPORTANT
In vehicles with active front steering, steering angle sensor adjustment is integrated in the service function "Initial operation/adjustment for active front steering" and must not be carried out separately!

NOTE:
Steering angle sensor adjustment must be carried out:
- After adjustment work on the front axle/steering
- After all mechanical work on the steering system
- After the following components have been replaced/coded
- Steering column switch cluster
- DSC control unit
- ARS control unit

Connect vehicle to BMW diagnosis system.
Select and carry out steering angle sensor adjustment under Service functions.""""

I found this post after a search for the steering angle sensor, pricey little bugger...
 
#41 · (Edited)
Here is a link to so you can see the steering column in an exploded view. You'll be looking at part "9". There are 3 different sensors steering angle sensors listed.
Steering column? The link didn't work so I went back to realoem after finding this short description of how to get to the right wheel sensor here

I found the parts location diagram for the ABS control unit but not for the set of "steering column" and "wheel" sensors yet. Yuck. There's even a sensor in the ABS unit itself (see number 3 below).

So how many sensors do we need to test anyway?

1. The 1 ABS "repair module" (in the passenger side of the engine compartment)
2. The 3 "steering angle" sensors (somewhere in the steering wheel)
3. The 4 ABS sensors in each of the four wheels (apparently the rear drivers side also controls the speedometer)
4. Any other sensors we need to look at?

REALOEM 2002 525i
34 BRAKES
34 05 FRONT WHEEL BRAKE
34 20 CONTROL SYSTEMS
Hydro unit DSC/control unit/fastening
01 Hydro unit DSC P/N:34516769536 $2,003.22
02 Repair kit, control unit DSC P/N:34526769862 $725.40
 

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#42 ·
#45 · (Edited)
Look guys, you all are speculating and associating completely unrelated stuff with the module and all that. Lets do this right and not just play musical parts. Borrow or buy a digital VOM (volt/ohm meter) from Menards. Make sure it has a diode check position. Ask the clerk if you are unsure of the diagram of a diode. You will check all four sensors at the Module. Very easy two wires to each sensor. With the meter in the diode position and checking the points I will tell you, you will get a reading of "open" or no display with the leads connected one way. You will then reverse the meter leads and you will get the opposite of whatever you got before. If you get a reading of 1.7 -1.8 volts you should get nothing (infinity) the other way. If you get infinity, reverse the leads and you should get 1.7 v-1.8v. The car should be completely off. You are reading the diode action in the sensor itself. If you get infinity with the leads both ways BINGO, you found the bad sensor. If all 4 sensors give open one way and a 1.7-1.8 volt drop the other way, the module is bad. Its that easy. Always better to rebuild your same module so you avoid having to have the dealer re-code a new module $100 for 5 min. work. ATE1234 on Ebay will rebuild your module for $105 and you get lifetime warranty and free return shipping. I will post the wires you want to check. When you remove the big connector at the module, look carefully and you will see the numbering scheme. The pins are so small you will insert paper clips into the correct terminals and then connect the meter leads to the paper clips.

rf= 15-16
lf= 12-28 These are the ABS module main connector pin numbers
rr= 30-31
lr= 13-29

If you find a bad sensor, remove the blue connector end of the speed sensor assm. Re-check the sensor there just like before there are two pins. put paper clips in being careful not to allow paper clips to touch one another. Test the sensor open/infinity in one direction and 1.78v in the other means the sensor is good and the wiring to the sensor or that blue connector connection is bad. Flush both sides with contain cleaner and reinstall. See if error is not clear. If you need more detail, please just ask. There are other things that can screw the system up like angle sensors and so forth, but the wheel speed/abs sensors by far are the more common (or the module). Try to re-build YOUR module. No recoding and even a new module will still be subject to heat failure just like your old one. A re-built will use bigger diodes and point-to-point wiring.
 
#1,130 ·
I've got a 2003 525i. Checked all four pairs at the connector and every one of them tests open. Used 2 different voltmeters on both diode and ohms scales. I used the diagnostic holes with paper clips and tried the actual holes using some breadboard wires the same size as the male plug, No go on any of them yet PA Soft shows not one bad wheel speed sensor. What the heck am I doing wrong ? Are these pins wired directly to the speed sensors or switched through ignition or some module or something or maybe different pins for my year ? The only manual I've found online so far left out the ELE wiring diagram.
 
#46 ·
540iman, Great write up, thanks. IMHO, pics added to your text would be great and worth sticking in the DIY section.
 
#47 ·
I'll do that if someone with some photo editing capability will take my raw pix and by working with me add some notes on the pics as to what we are looking at. You got it!

BTW, to ALL. FORGET the repair kit BMW mentions. I don't know if there even is such a thing anymore, but at the price you can just forget it. Also, these steering (yaw) sensors do feed the DSC/ABS module. They just don't seem to fail all that often so I have chosen to ignore them. They certainly can be a DSC/ABS/Brakes error cause, but they are expensive and only fail ever so often. If all speed sensors check ok, and the module has been re-built or appears ok and you still face an elusive error, then check with carsoft software or BMW GT-1 to verify
 
#48 · (Edited)
DIY ABS BRAKE DSC lights on (ABS Module & Wheel Sensor Test & Replace)

Here is my attempt at combining information for our ABS DIY repair writeup in a single post:
Credit: Extensive leverage from other sources; as new information comes in, I will update this post as long as it will let me.
Future: Maybe someone can put a copy of this in the DIY section after it's properly reviewed for mistakes.

CLASSIC ABS FAILURE SYMPTOMS:
- Most of the time, the problem is the ABS module or one of the 4 wheel speed sensors (& sometimes the brake pressure sensor)
- In my 2002 BMW E39 DSC, three orange (warning) cluster display lights lit, ABS, Brake, & DSC
- The 3 warning lights reset when the ignition is turned off, only to repeatedly reappear within minutes of normal driving
- The fault is often intermittent leading you to falsely believe you've resolved the problem (proper diagnosis is important)
- Sometimes the fault only appears when the engine is hot; other times only at speeds over 40 mph
- Carsoft may erroneously show a rear speed sensor failure; but just replacing the speed sensor may make no difference.
- All the work is in correct diagnosis of the problem; parts replacement is trivial (from 1 to six bolts in a few minutes)
- Hence, this BMW E39 ABS 3-warning light DIY will concentrate on understanding and diagnosis of the problem



FALSE ALARM SANITY CHECK:

If you recently drove on ice, a dynamometer, or on another very slippery surface, the car may just think the system has malfunctioned.
- Driving a few miles on a regular surface should fix the problem.
- Another fix is to slowly turn the steering wheel from completely left to completely right, then back again.
- The warning lights will reset whenever you turn the car off (but go back on if the fault persists)

BMW DESIGN PROBLEM:
- The E39 ABS module was mounted too close to engine heat causing solder cracks & fried electronics
- The 4 wheel sensors and wires are exposed to the elements and to shocks/vibration
- The 3 steering yaw sensors seem pretty well protected from both hazards but they may need recalibration
Note: Apparently newer-model BMWs moved the ABS module further away from engine heat (need confirmation)

FLOW CHART OF RECOMMENDED ACTIONS:
0) Watch, for a few days, speedo, odometer, tripmeter, cruise control, transmission, & ABS/BRAKE/DSC light activity
1) If ABS/BRAKE/DSC constantly comes back, test the 4 wheel sensor circuits from the ABS module connector
2) If any sensor circuit shows up as bad, test that specific sensor itself at that wheel (otherwise skip to step 5)
3) If the wheel sensor still shows up as bad, first remove, clean, grease, and re-install that sensor
4) If it still tests bad, then replace the sensor
...
5) If the sensors are good, test the ABS circuit with the Carsoft or Peake tools (or just assume a bad ABS module)
6) If the Carsoft or Peake tools indicate a different sensor, test & replace that sensor (e.g., pressure, yaw, acceleration, etc.)
7) Otherwise, assume your ABS module is the culprit (some say get your ABS module rebuilt anyway as it's going to go eventually)
...
8) If your ABS module is suspected, you have only the following 5 options:
- OPTION 0: You can do nothing and just not have ABS or DSC (not a good choice for anyone on this message board)
- OPTION 1: You can attempt a 3-part rebuild yourself (unfortunately we don't have enough information to help you yet)
- OPTION 2: You can send your module out for a rebuild (about 1/3 to 1/2 can be rebuilt but you'll have no speedo in the interim)
- OPTION 3: You can buy a rebuilt module (you'll have to add approximately $100 for a VIN recode at the dealer)
- OPTION 4: You can buy a brand new module (you'll again have to pay for a BMW dealership recoding to your VIN)
Note: Most people don't deal with testing the other 15 items; they just opt for sending their ABS module out to be rebuilt, which isn't necessarily a bad thing because generally it is the ABS and even if it isn't, some argue it's not a bad idea to rebuild even a working ABS.

READ THE SHOP MANUAL: ( http://www.bentleypublishers.com/isbn/9780837603179/index.html )
- For DSC pinouts, see Volume II, page ELE-15 of ABS/DSC controle module (A65) (2 sensors in the front and 2 in the rear)
- For ASC pinouts, see Volume II, page ELE-21 of ABS/ASC controle module (A52) (only 1 sensor in the front and 1 in the rear)
- For ABS/ASC/DSC system operation, see Volume I, page 300-12 (it's not all that useful though)
- For ABS/ASC/DSC system components, see Volume I, page 340-26 (again, not all that useful if you have this)

READ BMW MANUALS:
- Bosch DSC part 1, Bosch DSC part II (kindly supplied by Max_VQ)

READ THESE ARTICLES:
- http://www.meeknet.co.uk/E38/ABS/Index.htm
- http://forums.bimmerforums.com/forum/showthread.php?t=600452
- http://forums.bimmerforums.com/forum/showthread.php?t=1230488
- http://cparente.wordpress.com/2008/11/12/diy-the-answer-to-abs-problem/
- http://www.bimmerfest.com/forums/showthread.php?t=363554
- http://www.bimmerfest.com/forums/showthread.php?p=4202239#post4202239
etc.

UNDERSTAND DIGITAL MULTIMETER (DMM) TEST BASICS:
- http://www.allaboutcircuits.com/vol_3/chpt_3/2.html

GATHER SEAT-OF-THE-PANTS DATA:

- Note exactly which warning indicators are lit (e.g., ABS & BRAKE & DSC)
- Note whether cruise control is working or not (sometimes implicates the passenger-side rear sensor)
- Note whether the speedometer (hence odometer & tripmeter) is working (sometimes implicates the driver-side rear sensor)
- Note "free play", "dead spots", & "centering" of the steering wheel (sometimes implicates steering column sensors)
- Note if normal ABS pulsation (ABS working) or skidding (ABS not working) when hard braking on sandy shoulders at 15 mph
- Note if violent shudder (ABS working) or screech (ABS not working) when firm braking on top of speed bumps at 5mph
Note: It's not always just the sensor when the speedometer is also out with the 3 lights (the key is diagnosis)

ACKNOWLEDGE ALL POSSIBLE (20) & MOST LIKELY (2) CULPRITS:
• 1 BOSCH DC III Control Module 83 Pin (combined with the hydraulic unit in my E39, DSC III Bosch 5.7) <==COMMON CULPRIT!
• 1 Hydraulic Unit (combined with the control module in my E39, DSC III Bosch 5.7)
• Hydraulic Unit contains: 2 pre-charge solenoid valves
• Hydraulic Unit contains: 2 changeover solenoid valves
• Hydraulic Unit contains: 4 intake solenoid valves
• Hydraulic Unit contains: 4 outlet solenoid valves
• Hydraulic Unit contains: 1 return pump
• 2 Front Wheel Speed Sensors (Active Hall Effect) in the steering knuckles, secured with two 4 mm allen bolts <==COMMON CULPRIT!
• 2 Rear Wheel Speed Sensors (Active Hall Effect) in the rear wheel bearing carriers, secured with one 4 mm allen bolt <==COMMON CULPRIT!
• 1 Hydraulic Pressure Sensor (attached to the front-brake hydraulic unit in my E39, DSC III Bosch 5.7) <==MY PROBLEM!
• 1 Steering Angle Sensor (located in the bottom of the steering column, near the flexible coupling)
• 1 Rotation Rate, aka Yaw Sensor (combined with the lateral-acceleration sensor in my E39, DSC III Bosch 5.7)
• 1 Lateral Acceleration Sensor (combined with the yaw sensor in my E39, DSC III Bosch 5.7)
• 1 DSC Switch (located below the radio in the cockpit)
• 1 Hand Brake Switch (located on the hand brake assembly)
• 1 Brake Switch (located on the brake-pedal assembly)
• 1 Pre-Charging Pump
• 1 Charging Piston (750iL only)

PHOTOGRAPH OF THE MOST LIKELY CULPRITS:

GATHER DESIRED TOOLS:
- Print this DIY out, bring a pencil to mark down your readings, and a drink
- Digital multi meter (DMM) with a diode-test capability & long, very narrow probes
- About six inches of 20 AWG stiff wire (to attach to your DMM probes and to the female ABS connector)
- A small piece of white or yellow tape so that you can label the positive stiff wire (to avoid confusion with the negative probe)
- T20 six-point Torx bit in a 1/4" socket with a 6" extension for removing the ABS control module
- 4mm allen wrench for removing the front wheel sensors
- Torque wrench (see torque tables below) for replacing components
- For rear sensors, a 10 mm socket, 8 mm socket, flat-head screwdriver, and needle-nose pliers might be required to remove trim.
- 1/4-inch wide 6-inch long standard flathead screwdriver for removing ABS harness connector clip
- CRC cleaner (or equivalent brake cleaner)
- Staburags NBU 12/K or equivalent grease (for speed sensors and connections in the housings)

GATHER OPTIONAL TOOLS:

- (maybe) 10mm socket for removing air filter box (easier access for some E39 models)
- Carsoft 6.5 or Peake Research or equivalent OBDII diagnostic scanner
- Oscilloscope (look for millivolt square waves coming from powered sensors as the wheel turns)
- Note: Carsoft 6.5 can't perform encoding, activation, or steering adjustments.
- Note: Bad ABS modules often report erroneous indications of a bad RR sensor in the OBD scanner reports
- Note: You must use new bolts for the ABS Control Module (according to the Bentleys)


PRICE OEM PARTS:

- Repair kit, control unit DSC, $1,120 + $112 (~10% tax) = $1,232 (often colloquially referred to as the "ABS control unit")
- Wheel sensors, front, $134 x 2 = $268 + $27 (~10% tax) = $295 total (some suggested EAC tuning for wheel sensors)
- Wheel sensors rear, $201 x 2 = = $402 + $40 (~10% tax) = $442 total (some suggested AutoHauz for wheel sensors)
- Front brake pressure sensor, $111 + 10% tax = ~$125 (measures 0-250bars of front-brake pressure, outputs 0-5 volts)
- Steering angle (yaw) sensors (in the steering wheel column or under driver's seat) ~$250 each (almost never needed)
- Hydro unit, DSC, $2,003 x 1 + $200 (~10% tax) = $2,013 (this "hydro unit" behind the ABS control unit is almost never at fault)
Note: If you replace the ABS module, you'll also need a $100 dealership recoding to your VIN & steering angles calibrated (apparently)

PRICE REBUILDING OF YOUR ABS MODULE:
- Module Masters ($105) http://www.modulemaster.com/en/abs/ate_bmw_asc.php
- BBA Remanufacturing (8 days, $225) http://www.bba-reman.com
- Auto & Truck Electronics ($105) EBAY seller's ID ATE1234, lifetime warranty, free shipping, quick turnaround
- Note: A rebuild of your ABS unit won't require VIN coding, activation, or steering angle calibration

PRICE A REBUILT ABS MODULE FROM ANOTHER VEHICLE:
- For a rebuilt part, most suggest oembimmerparts.com, one of our sponsors, at about $450 + $45 tax = $500
- Note: A rebuilt ABS unit from another vehicle requires a $100 dealership VIN recoding effort
QUESTION: What happens if you don't code the VIN & check steering angles ... (does the car blow up?)

CONSIDER FIXING IT YOURSELF (we need much more details to make this option viable):
- Open up the module & look for broken solder joints which can be sucked and resoldered (take pictures)
- Add point-to-point wiring where needed (we need more information to make this actionable)
- Replace diodes and any other weak parts with more robust parts (again, not very useful unless we know exactly what)
- Post before and after pictures so each of us can learn from the rest

CHECK BMW ERROR CODES:
- Locate the OBDII port, by law, in the cockpit, within 3 feet of the driver (above the driver's left knee in American BMWs)
- Hook up Carsoft or Peake diagnostic tools to the OBDII port to determine any error codes
- Cross reference Carsoft error codes with the list of Bosch 5.7 error codes listed bellow (kindly supplied by Max_VQ)
Note: Some say this check is of dubious value because a bad ABS module may show up as a bad rear sensor; always test the sensor itself!

BMW ABS/ASC Bosch 5.7 Table of error codes:
5 Right Rear Wheel Speed Sensor
6 Right Front Wheel Speed Sensor
7 Front Left Wheel Speed Sensor
14 Solenoid Valve Relay (check fuses 17 & 33)
15 Pressure Sensor/Pump Error
21 Module Memory Failure - ABS/ASC module is faulty
23 Incorrect Coding - ABS/ASC module is faulty
24 Wrong Impulse
30 Left Rear Wheel Speed Sensor
31 Open Right Rear Wheel Speed Sensor
32 Open Right Front Wheel Speed Sensor
33 Open Left Front Wheel Speed Sensor
50 Right Front Outlet Valve - ABS/ASC module is faulty
51 Left Rear Outlet Valve - ABS/ASC module is faulty
54 Left Front Inlet Valve - ABS/ASC module is faulty
55 ASC Intake Valve - ABS/ASC module is faulty
58 Gear Box Control Unit (CAN bus error)
59 DMER1 (CAN bus error)
61 Steering Angle Sensor Identification
66 Speed Sensor Voltage Supply
67 Intermittent Interference
75 Engine Speed Fault from DME
81 Pressure Sensor
82 Open Yaw Rate Sensor
86 ASC Cut-off Valve Rear Axle
88 Precharge Pump
89 Low Voltage
90 Temporary System Deactivation
94 DDE Fault/Yaw rate sensor
97 Steering Angle Sensor
10 Brake Light Switch
108 SN Control
112 Open CAN to Instrument Cluster
114 Pressure Sensor Offset
117 Brake Light Switch Failure
118 DME Status-Internal Error

REMOVE ABS-MODULE CONNECTOR:
- Facing the engine, slide the plastic retaining clip to the right with a 1/4 inch flathead screwdriver.
- It is a plastic retaining clip, so do be careful not to break it; it slides over about 1 1/4 inches or so.
- Once the clip is fully to the right, lift the electrical connector up
- Notice the female (blue) connector with 42 holes (and very tiny lettering)
- DO NOT STICK YOUR TEST LEAD INTO THE SQUARE HOLES!
(Only put test leads into the larger rectangular holes next to the square holes.)


NOTE ABS-MODULE PINOUT: (notice the test lead holes)
- Each wheel sensor circuit has a set of two wires in the ABS connector (pinout kindly supplied by 540iman)
- ABS-connector pins 13,29 = Left rear wheel sensor (also affects speedometer & odometer & tripmeter)
- ABS-connector pins 30,31 = Right rear wheel sensor (also affects cruise control)
- ABS-connector pins 28,12 = Left front wheel sensor (some say it also acts as a steering angle sensor)
- ABS-connector pins 15,16 = Right front wheel sensor (tells gearbox electronics how fast you're going)
Note: These pinouts are in the same order of the diode action of each sensor (do not reverse these numbers)
Note: Don't confuse with the brake pad wear sensor, which is only located on the front left & rear right wheel & which uses a black connector.
Note: ASC cars have only two sensors, one on the front right and the other on the rear left wheel.


UNDERSTAND WHEEL SPEED SENSORS:
Note: The wheel speed sensors are two-wire hall effect transducers which send a digital square wave signal with a low of .75 volts and a high of 2.5 volts to the DSC control unit. Each sensor receives a well-regulated 8 volt power supply from the control module through one wire. The ground path for the sensor is through the second wire back to the control module. The signal is generated by a pulse wheel affecting the voltage flow through the hall element in the sensor. The pulse wheel is integrated into the wheel bearing assembly, behind the seal. This protects the trigger wheel from foreign substances which may affect the wheel speed signal.

TEST WHEEL SENSOR CIRCUIT FROM THE ABS CONNECTOR
(also checks wiring circuit):
OPTIONAL: Jack car up (so that all four wheels can be spun to test voltage & resistance fluctuations of the hall-effect sensors)
- Turn the car off and remove the key from the ignition.
- TEST 1: Switch the DMM into the diode test position
- Wrap a stiff 20AWG wire onto the ends of your DMM probe for sticking into ABS-connector pins
- Label the positive 20AWG wire with white tape so that you won't get confused as you switch back and forth
- Stick the ends of the wire into the appropriate female holes of the ABS connector (13-29, 30-31, 28-12, 15-16)
- In one direction, you should see 1.7 to 1.8 volts (note the pinouts mentioned are in order, positive to negative)
- In the other direction, you should see OL or some other infinite reading (open circuit)
- TEST 2: Switch the DMM into resistance checking mode (optional)
- You should see around 3.3 Mega ohms in one direction & approximately twice that in the other direction (but some say more)
- TEST 3: If desired spin the wheel at about 1 revolution per second, by hand (the resistance should fluctuate as the wheel spins)
- TEST 4: Switch the DMM into millivolt mode (optional) & again spin the tire & wheel assembly by hand (test-lead polarity won't matter)
- You should read between 1 and 5 mV when you spin the hub (no voltage implicate the sensor or circuit)
- OPTIONAL TESTS BELOW REQUIRE FLYING LEADS WITH THE IGNITION SYSTEM ABS SYSTEM CONNECTED & POWERED UP:
- TEST 5: Swith the DMM into the 10v and attach flying leads to the sensors with the power on
- You should see the voltage going to the sensor and the return signal
- Expect a baseline voltage of about +5 to +12 volts depending on the ABS system (does anyone know this value?)
- Expect that baseline voltage to the sensor to change (by how much?) as you spin the wheels
- TEST 6: Hook an oscilloscope with "flying leads" to the ABS sensors (notice that the ABS system must be powered)
- You should see nice clean square waves generated as you hand spin the wheels at about 1 revolution per second.
Note: The oscilliscope can detect problems that can't easily be found with a DMM (A scope pattern for a wheel speed sensor should show a classic sine wave alternating current pattern that changes both in frequency and amplitude with wheel speed. As the wheel is turned faster, signal frequency and amplitude should both increase. Damaged or missing teeth on the sensor ring will show up as flat spots or gaps in the sine wave pattern. A bent axle or hub will produce an undulating pattern that changes as the strength of the sensor signal changes with every revolution. If the scope pattern produced by the sensor is flattened (diminished amplitude) or is erratic, it usually indicates a weak signal caused by an excessively wide air gap between the tip of the sensor and its ring, or a buildup of metallic debris on the end of the sensor. A weak signal can also be caused by internal resistance in the sensor or its wiring circuit, or loose or corroded wiring connectors.)


INTERPRET DIODE-TEST RESULTS:
- If the DMM, in diode mode, reads infinity ("OL") in both directions, you've got a bad sensor or circuit
- If the DMM, in resistance mode, reads much greater than 7Mohms, you've got a bad sensor or circuit
- If all 4 sensors read OK, it's most likely the ABS control unit.
- If you think you found two bad sensors, you probably messed up.
- Rarely is the cause due to bad steering angle (yaw/lew) sensors
- Rarely is the cause due to a bad hydro unit
- The problem is almost always a wheel rotation sensor or the ABS control unit

ACTUAL RESULTS ON MY 2002 E39 THIS MEMORIAL DAY WEEKEND:


DOUBLECHECK WHEEL SENSORS AT THE WHEEL:
Note: You can run this test w/o removing the wheel but access to the sensor connector is easier with the wheels off the E39
- If one or more sensor circuits test bad in any of the three tests above ... then ...
- Locate the sensor blue connector in the rear of each front wheel well by turning the front wheels
- Easiest to first locate the sensor (bolted on the wheel carrier near the hub) and trace its wire back to a black plastic hinged box housing
- Open the locked hinged plastic rectangular black box with a small flathead screwdriver
- Locate the blue wheel sensor connector (next to a black brake wear sensor connector)
- Pull the blue wheel sensor connector out of the box and disconnect the two sides
- Re-check the sensor there with the diode function of the DMM



CHECK WHEEL SENSORS OFF THE VEHICLE:
- If any sensor still checks bad, pull the sensor off the vehicle for a closer inspection
- Chock wheels and jack E39 BMW and jack stand at the 4 jack pad locations
- Remove 4mm allen head bolts to sensor retention screw (two retaining bolts for fronts, 1 bolt for the rears)
- Pull wheel sensor out of hub assembly, straight up.
- Clean with CRC electronic cleaner
- Check with DMM diode-test meter as before
- Grease with Staburags NBU 12/K or equivalent grease
- Replace sensor back into hub assembly, snug tighten to 6 foot pounds
- Replace rear wheel, tighten to 82 to 96 foot pounds
Note: You might wish to swap sensors on the same axle when replacing so as to obtain further diagnostic information should an anomaly occur.
Note: Here is a picture of a dirty and cleaned sensor (magnetic particle buildup)



TEST BRAKE PRESSURE SENSOR (aka HYDRAULIC UNIT PRESSURE SENSOR):
- This test procedure kindly suggested by Max_VQ:
- Given 250 bar = 3,626 psi, and given 0-5 volts linear proportional output, 3,626 psi/ 5v = 725.2 psi/volt or 1.3 mV per psi.
- With the ignition on, measure the voltage on the pressure sensor while someone is pressing hard on the brake pedal
- My guess is that should create about 3,000 psi of force and should show around 4.13 volts.
- At rest it should show very close to 0 volts
Note: The front-brake pressure sensor provides a 0-5 volt linear voltage signal to the DSC III control module which is proportionate to how hard the driver is pressing on the brake pedal, from zero to 250 bars (3,626 psi), spanning (a) no braking, to (b) partial braking, and to (c) near-ABS-regulation state braking. This brake pressure sensor has three pins (a) power, (b) ground and (c) the 0-5 volt proportionate signal.
Note: By way of comparison, the Corvette also has a brake pressure sensor to indicate how hard the brakes are being applied; it monitors pressure from 0 to 2000psi generating a corresponding signal of 0.20 volts to 4.80 volts.

LOCATION OF FRONT-BRAKE PRESSURE SENSOR:
• DSC III 5.3 (740i/iL and 540i) - The brake pressure sensor is located in the charge pump assembly.
• DSC III 5.3 (750iL) - The sensor is located on the charge piston unit.
• DSC III 5.7 (ALL) - The sensor is located on the hydraulic unit on my 2002 E39.


TEST ROTATION RATE & LATERAL ACCELERATION SENSOR:
- We do not yet have a test for this sensor; a description of operation is all we have at the moment (please suggest a test procedure so all benefit)
- On Bosch DSC III (Bosch 5.7) the Rotation Rate sensor (yaw) and the Lateral Acceleration sensor have been combined into one unit located under the drivers seat under the carpet
- The degree of rotation rate (yaw) transducer outputs a reference signal of 2.5 volts and a linear voltage of 0.7 to 4.3 volts
- The lateral acceleration output signal should be 1.7 volts while the car is sitting still on a flat surface corresponding to 0 G side forces.
- The lateral acceleration transducer outputs a linear voltage of 0.5 to 4.5 volts corresponding to a G-Force range of -1.5 to +3.5 G side forces depending on the motion of a fixed capacitor plate relative to a floating capacitor plate.


TEST STEERING ANGLE SENSOR:
- We don't yet know how to test the steering-angle sensor (please advise)
Note: The steering angle sensor, mounted at the bottom of the steering column near the flexible coupling, utilizes two potentiometers to determine the steering angle and the rate of steering angle change, which are are the two raw signals the CAN bus microprocessor utilizes to create the steering angle signal for broadcast over the CAN bus. The DSC III logic compares the stored plausibility of the steering angle sensor against other DSC III inputs (front wheel speeds, rotation rate and lateral acceleration sensors).

STEERING ANGLE SENSOR:


REMOVE ABS MODULE:
- Remove the six T20 Torx screws holding the ABS module to the hydro unit
- Pull the ABS module straight out towards the passenger side headlight.
- Cover the hydro unit with aluminum foil to protect it from the elements
- You can drive the car but you won't have a speedometer or odometer
- Use a portable GPS unit with a speed display as your temporary speedometer
- You may not have cruise control (need to test this)
- Of course, you won't have ABS either but you didn't have that anyway

HINTS TO HELP OTHERS:
- Consider taking apart your ABS module and posting before rebuild and after rebuild pictures
- Consider paying rebuilders the extra $10 to return ABS modules that failed (so you can take it apart & post pictures)
- Consider selling your old module to the rebuilders if you buy a new or rebuilt ABS module from another vehicle
- A portable GPS unit doubles as a speedometer in the interim while your ABS module is being rebuilt

REINSTALL ABS MODULE:
- Note: There is a gasket attached to the new unit.
- Carefully place the new module over the control actuators.
- Loosely replace the six new T20 Torx screws included with the new module.
- Tighten snug tight, and then a little more to seat the gasket.
- Reposition the ABS electrical connector
- Press down on the ABS connector while pushing the retaining clip to the left
- Reassemble the Air Filter box & MAF (if it was disassembled for Torx access).

INITIALIZE ABS MODULES:

- Note: This step is only necessary if you installed an ABS module that wasn't originally in the car in the first place
- Take the E39 to an Indy to encode the VIN (I'm not sure what happens if you don't do this)
- Take the E39 to an Indy to check and adjust the steering angle (I'm not sure why)
- Some say the steering angle sensor may have to be recalibrated when you put on a remanufactured or new ABS module.

TORQUE TABLE:
- 4mm wheel sensor bolts (two each for the front sensors, 1 each for the rear sensors) = 6 foot pounds
- Combination lateral acceleration/rotational rate sensor (under driver seat) = 6 foot pounds
- DSC bolts to the hydraulic unit (new bolts only) = 26 inch pounds
- Hydraulic unit to body = 6 foot pounds
- Hydraulic unit mounting bracket = 6 foot pounds
- Brake lines to hydraulic unit = 13 foot pounds
- Wheel lug nuts = 82 to 96 foot pounds

DIAGRAM OF THE 2002 E39 DSC III BOSCH 5.7 SYSTEM:


USE THIS CHART TO DETERMINE WHICH ABS SYSTEM YOU HAVE:


Note: This ABS repair thread was compiled from scores of sources; special credit goes to many people, especially 540iman, BlackBMWs, Max_VQ, Edgy36-39, and others.
 

Attachments

#766 ·
Here is my attempt at combining information for our ABS DIY repair writeup in a single post:
Credit: Extensive leverage from other sources; as new information comes in, I will update this post as long as it will let me.
Future: Maybe someone can put a copy of this in the DIY section after it's properly reviewed for mistakes.

CLASSIC ABS FAILURE SYMPTOMS:
- Most of the time, the problem is the ABS module or one of the 4 wheel speed sensors (& sometimes the brake pressure sensor)
- In my 2002 BMW E39 DSC, three orange (warning) cluster display lights lit, ABS, Brake, & DSC
- The 3 warning lights reset when the ignition is turned off, only to repeatedly reappear within minutes of normal driving
- The fault is often intermittent leading you to falsely believe you've resolved the problem (proper diagnosis is important)
- Sometimes the fault only appears when the engine is hot; other times only at speeds over 40 mph
- Carsoft may erroneously show a rear speed sensor failure; but just replacing the speed sensor may make no difference.
- All the work is in correct diagnosis of the problem; parts replacement is trivial (from 1 to six bolts in a few minutes)
- Hence, this BMW E39 ABS 3-warning light DIY will concentrate on understanding and diagnosis of the problem



FALSE ALARM SANITY CHECK:

If you recently drove on ice, a dynamometer, or on another very slippery surface, the car may just think the system has malfunctioned.
- Driving a few miles on a regular surface should fix the problem.
- Another fix is to slowly turn the steering wheel from completely left to completely right, then back again.
- The warning lights will reset whenever you turn the car off (but go back on if the fault persists)

BMW DESIGN PROBLEM:
- The E39 ABS module was mounted too close to engine heat causing solder cracks & fried electronics
- The 4 wheel sensors and wires are exposed to the elements and to shocks/vibration
- The 3 steering yaw sensors seem pretty well protected from both hazards but they may need recalibration
Note: Apparently newer-model BMWs moved the ABS module further away from engine heat (need confirmation)

FLOW CHART OF RECOMMENDED ACTIONS:
0) Watch, for a few days, speedo, odometer, tripmeter, cruise control, transmission, & ABS/BRAKE/DSC light activity
1) If ABS/BRAKE/DSC constantly comes back, test the 4 wheel sensor circuits from the ABS module connector
2) If any sensor circuit shows up as bad, test that specific sensor itself at that wheel (otherwise skip to step 5)
3) If the wheel sensor still shows up as bad, first remove, clean, grease, and re-install that sensor
4) If it still tests bad, then replace the sensor
...
5) If the sensors are good, test the ABS circuit with the Carsoft or Peake tools (or just assume a bad ABS module)
6) If the Carsoft or Peake tools indicate a different sensor, test & replace that sensor (e.g., pressure, yaw, acceleration, etc.)
7) Otherwise, assume your ABS module is the culprit (some say get your ABS module rebuilt anyway as it's going to go eventually)
...
8) If your ABS module is suspected, you have only the following 5 options:
- OPTION 0: You can do nothing and just not have ABS or DSC (not a good choice for anyone on this message board)
- OPTION 1: You can attempt a 3-part rebuild yourself (unfortunately we don't have enough information to help you yet)
- OPTION 2: You can send your module out for a rebuild (about 1/3 to 1/2 can be rebuilt but you'll have no speedo in the interim)
- OPTION 3: You can buy a rebuilt module (you'll have to add approximately $100 for a VIN recode at the dealer)
- OPTION 4: You can buy a brand new module (you'll again have to pay for a BMW dealership recoding to your VIN)
Note: Most people don't deal with testing the other 15 items; they just opt for sending their ABS module out to be rebuilt, which isn't necessarily a bad thing because generally it is the ABS and even if it isn't, some argue it's not a bad idea to rebuild even a working ABS.

READ THE SHOP MANUAL: ( http://www.bentleypublishers.com/isbn/9780837603179/index.html )
- For DSC pinouts, see Volume II, page ELE-15 of ABS/DSC controle module (A65) (2 sensors in the front and 2 in the rear)
- For ASC pinouts, see Volume II, page ELE-21 of ABS/ASC controle module (A52) (only 1 sensor in the front and 1 in the rear)
- For ABS/ASC/DSC system operation, see Volume I, page 300-12 (it's not all that useful though)
- For ABS/ASC/DSC system components, see Volume I, page 340-26 (again, not all that useful if you have this)

READ BMW MANUALS:
- Bosch DSC part 1, Bosch DSC part II (kindly supplied by Max_VQ)

READ THESE ARTICLES:
- http://www.meeknet.co.uk/E38/ABS/Index.htm
- http://forums.bimmerforums.com/forum/showthread.php?t=600452
- http://forums.bimmerforums.com/forum/showthread.php?t=1230488
- http://cparente.wordpress.com/2008/11/12/diy-the-answer-to-abs-problem/
- http://www.bimmerfest.com/forums/showthread.php?t=363554
- http://www.bimmerfest.com/forums/showthread.php?p=4202239#post4202239
etc.

UNDERSTAND DIGITAL MULTIMETER (DMM) TEST BASICS:
- http://www.allaboutcircuits.com/vol_3/chpt_3/2.html

GATHER SEAT-OF-THE-PANTS DATA:

- Note exactly which warning indicators are lit (e.g., ABS & BRAKE & DSC)
- Note whether cruise control is working or not (sometimes implicates the passenger-side rear sensor)
- Note whether the speedometer (hence odometer & tripmeter) is working (sometimes implicates the driver-side rear sensor)
- Note "free play", "dead spots", & "centering" of the steering wheel (sometimes implicates steering column sensors)
- Note if normal ABS pulsation (ABS working) or skidding (ABS not working) when hard braking on sandy shoulders at 15 mph
- Note if violent shudder (ABS working) or screech (ABS not working) when firm braking on top of speed bumps at 5mph
Note: It's not always just the sensor when the speedometer is also out with the 3 lights (the key is diagnosis)

ACKNOWLEDGE ALL POSSIBLE (20) & MOST LIKELY (2) CULPRITS:
• 1 BOSCH DC III Control Module 83 Pin (combined with the hydraulic unit in my E39, DSC III Bosch 5.7) <==COMMON CULPRIT!
• 1 Hydraulic Unit (combined with the control module in my E39, DSC III Bosch 5.7)
• Hydraulic Unit contains: 2 pre-charge solenoid valves
• Hydraulic Unit contains: 2 changeover solenoid valves
• Hydraulic Unit contains: 4 intake solenoid valves
• Hydraulic Unit contains: 4 outlet solenoid valves
• Hydraulic Unit contains: 1 return pump
• 2 Front Wheel Speed Sensors (Active Hall Effect) in the steering knuckles, secured with two 4 mm allen bolts <==COMMON CULPRIT!
• 2 Rear Wheel Speed Sensors (Active Hall Effect) in the rear wheel bearing carriers, secured with one 4 mm allen bolt <==COMMON CULPRIT!
• 1 Hydraulic Pressure Sensor (attached to the front-brake hydraulic unit in my E39, DSC III Bosch 5.7) <==MY PROBLEM!
• 1 Steering Angle Sensor (located in the bottom of the steering column, near the flexible coupling)
• 1 Rotation Rate, aka Yaw Sensor (combined with the lateral-acceleration sensor in my E39, DSC III Bosch 5.7)
• 1 Lateral Acceleration Sensor (combined with the yaw sensor in my E39, DSC III Bosch 5.7)
• 1 DSC Switch (located below the radio in the cockpit)
• 1 Hand Brake Switch (located on the hand brake assembly)
• 1 Brake Switch (located on the brake-pedal assembly)
• 1 Pre-Charging Pump
• 1 Charging Piston (750iL only)

PHOTOGRAPH OF THE MOST LIKELY CULPRITS:

GATHER DESIRED TOOLS:
- Print this DIY out, bring a pencil to mark down your readings, and a drink
- Digital multi meter (DMM) with a diode-test capability & long, very narrow probes
- About six inches of 20 AWG stiff wire (to attach to your DMM probes and to the female ABS connector)
- A small piece of white or yellow tape so that you can label the positive stiff wire (to avoid confusion with the negative probe)
- T20 six-point Torx bit in a 1/4" socket with a 6" extension for removing the ABS control module
- 4mm allen wrench for removing the front wheel sensors
- Torque wrench (see torque tables below) for replacing components
- For rear sensors, a 10 mm socket, 8 mm socket, flat-head screwdriver, and needle-nose pliers might be required to remove trim.
- 1/4-inch wide 6-inch long standard flathead screwdriver for removing ABS harness connector clip
- CRC cleaner (or equivalent brake cleaner)
- Staburags NBU 12/K or equivalent grease (for speed sensors and connections in the housings)

GATHER OPTIONAL TOOLS:

- (maybe) 10mm socket for removing air filter box (easier access for some E39 models)
- Carsoft 6.5 or Peake Research or equivalent OBDII diagnostic scanner
- Oscilloscope (look for millivolt square waves coming from powered sensors as the wheel turns)
- Note: Carsoft 6.5 can't perform encoding, activation, or steering adjustments.
- Note: Bad ABS modules often report erroneous indications of a bad RR sensor in the OBD scanner reports
- Note: You must use new bolts for the ABS Control Module (according to the Bentleys)


PRICE OEM PARTS:

- Repair kit, control unit DSC, $1,120 + $112 (~10% tax) = $1,232 (often colloquially referred to as the "ABS control unit")
- Wheel sensors, front, $134 x 2 = $268 + $27 (~10% tax) = $295 total (some suggested EAC tuning for wheel sensors)
- Wheel sensors rear, $201 x 2 = = $402 + $40 (~10% tax) = $442 total (some suggested AutoHauz for wheel sensors)
- Front brake pressure sensor, $111 + 10% tax = ~$125 (measures 0-250bars of front-brake pressure, outputs 0-5 volts)
- Steering angle (yaw) sensors (in the steering wheel column or under driver's seat) ~$250 each (almost never needed)
- Hydro unit, DSC, $2,003 x 1 + $200 (~10% tax) = $2,013 (this "hydro unit" behind the ABS control unit is almost never at fault)
Note: If you replace the ABS module, you'll also need a $100 dealership recoding to your VIN & steering angles calibrated (apparently)

PRICE REBUILDING OF YOUR ABS MODULE:
- Module Masters ($105) http://www.modulemaster.com/en/abs/ate_bmw_asc.php
- BBA Remanufacturing (8 days, $225) http://www.bba-reman.com
- Auto & Truck Electronics ($105) EBAY seller's ID ATE1234, lifetime warranty, free shipping, quick turnaround
- Note: A rebuild of your ABS unit won't require VIN coding, activation, or steering angle calibration

PRICE A REBUILT ABS MODULE FROM ANOTHER VEHICLE:
- For a rebuilt part, most suggest oembimmerparts.com, one of our sponsors, at about $450 + $45 tax = $500
- Note: A rebuilt ABS unit from another vehicle requires a $100 dealership VIN recoding effort
QUESTION: What happens if you don't code the VIN & check steering angles ... (does the car blow up?)

CONSIDER FIXING IT YOURSELF (we need much more details to make this option viable):
- Open up the module & look for broken solder joints which can be sucked and resoldered (take pictures)
- Add point-to-point wiring where needed (we need more information to make this actionable)
- Replace diodes and any other weak parts with more robust parts (again, not very useful unless we know exactly what)
- Post before and after pictures so each of us can learn from the rest

CHECK BMW ERROR CODES:
- Locate the OBDII port, by law, in the cockpit, within 3 feet of the driver (above the driver's left knee in American BMWs)
- Hook up Carsoft or Peake diagnostic tools to the OBDII port to determine any error codes
- Cross reference Carsoft error codes with the list of Bosch 5.7 error codes listed bellow (kindly supplied by Max_VQ)
Note: Some say this check is of dubious value because a bad ABS module may show up as a bad rear sensor; always test the sensor itself!

BMW ABS/ASC Bosch 5.7 Table of error codes:
5 Right Rear Wheel Speed Sensor
6 Right Front Wheel Speed Sensor
7 Front Left Wheel Speed Sensor
14 Solenoid Valve Relay (check fuses 17 & 33)
15 Pressure Sensor/Pump Error
21 Module Memory Failure - ABS/ASC module is faulty
23 Incorrect Coding - ABS/ASC module is faulty
24 Wrong Impulse
30 Left Rear Wheel Speed Sensor
31 Open Right Rear Wheel Speed Sensor
32 Open Right Front Wheel Speed Sensor
33 Open Left Front Wheel Speed Sensor
50 Right Front Outlet Valve - ABS/ASC module is faulty
51 Left Rear Outlet Valve - ABS/ASC module is faulty
54 Left Front Inlet Valve - ABS/ASC module is faulty
55 ASC Intake Valve - ABS/ASC module is faulty
58 Gear Box Control Unit (CAN bus error)
59 DMER1 (CAN bus error)
61 Steering Angle Sensor Identification
66 Speed Sensor Voltage Supply
67 Intermittent Interference
75 Engine Speed Fault from DME
81 Pressure Sensor
82 Open Yaw Rate Sensor
86 ASC Cut-off Valve Rear Axle
88 Precharge Pump
89 Low Voltage
90 Temporary System Deactivation
94 DDE Fault/Yaw rate sensor
97 Steering Angle Sensor
10 Brake Light Switch
108 SN Control
112 Open CAN to Instrument Cluster
114 Pressure Sensor Offset
117 Brake Light Switch Failure
118 DME Status-Internal Error

REMOVE ABS-MODULE CONNECTOR:
- Facing the engine, slide the plastic retaining clip to the right with a 1/4 inch flathead screwdriver.
- It is a plastic retaining clip, so do be careful not to break it; it slides over about 1 1/4 inches or so.
- Once the clip is fully to the right, lift the electrical connector up
- Notice the female (blue) connector with 42 holes (and very tiny lettering)
- DO NOT STICK YOUR TEST LEAD INTO THE SQUARE HOLES!
(Only put test leads into the larger rectangular holes next to the square holes.)


NOTE ABS-MODULE PINOUT: (notice the test lead holes)
- Each wheel sensor circuit has a set of two wires in the ABS connector (pinout kindly supplied by 540iman)
- ABS-connector pins 13,29 = Left rear wheel sensor (also affects speedometer & odometer & tripmeter)
- ABS-connector pins 30,31 = Right rear wheel sensor (also affects cruise control)
- ABS-connector pins 28,12 = Left front wheel sensor (some say it also acts as a steering angle sensor)
- ABS-connector pins 15,16 = Right front wheel sensor (tells gearbox electronics how fast you're going)
Note: These pinouts are in the same order of the diode action of each sensor (do not reverse these numbers)
Note: Don't confuse with the brake pad wear sensor, which is only located on the front left & rear right wheel & which uses a black connector.
Note: ASC cars have only two sensors, one on the front right and the other on the rear left wheel.


UNDERSTAND WHEEL SPEED SENSORS:
Note: The wheel speed sensors are two-wire hall effect transducers which send a digital square wave signal with a low of .75 volts and a high of 2.5 volts to the DSC control unit. Each sensor receives a well-regulated 8 volt power supply from the control module through one wire. The ground path for the sensor is through the second wire back to the control module. The signal is generated by a pulse wheel affecting the voltage flow through the hall element in the sensor. The pulse wheel is integrated into the wheel bearing assembly, behind the seal. This protects the trigger wheel from foreign substances which may affect the wheel speed signal.

TEST WHEEL SENSOR CIRCUIT FROM THE ABS CONNECTOR
(also checks wiring circuit):
OPTIONAL: Jack car up (so that all four wheels can be spun to test voltage & resistance fluctuations of the hall-effect sensors)
- Turn the car off and remove the key from the ignition.
- TEST 1: Switch the DMM into the diode test position
- Wrap a stiff 20AWG wire onto the ends of your DMM probe for sticking into ABS-connector pins
- Label the positive 20AWG wire with white tape so that you won't get confused as you switch back and forth
- Stick the ends of the wire into the appropriate female holes of the ABS connector (13-29, 30-31, 28-12, 15-16)
- In one direction, you should see 1.7 to 1.8 volts (note the pinouts mentioned are in order, positive to negative)
- In the other direction, you should see OL or some other infinite reading (open circuit)
- TEST 2: Switch the DMM into resistance checking mode (optional)
- You should see around 3.3 Mega ohms in one direction & approximately twice that in the other direction (but some say more)
- TEST 3: If desired spin the wheel at about 1 revolution per second, by hand (the resistance should fluctuate as the wheel spins)
- TEST 4: Switch the DMM into millivolt mode (optional) & again spin the tire & wheel assembly by hand (test-lead polarity won't matter)
- You should read between 1 and 5 mV when you spin the hub (no voltage implicate the sensor or circuit)
- OPTIONAL TESTS BELOW REQUIRE FLYING LEADS WITH THE IGNITION SYSTEM ABS SYSTEM CONNECTED & POWERED UP:
- TEST 5: Swith the DMM into the 10v and attach flying leads to the sensors with the power on
- You should see the voltage going to the sensor and the return signal
- Expect a baseline voltage of about +5 to +12 volts depending on the ABS system (does anyone know this value?)
- Expect that baseline voltage to the sensor to change (by how much?) as you spin the wheels
- TEST 6: Hook an oscilloscope with "flying leads" to the ABS sensors (notice that the ABS system must be powered)
- You should see nice clean square waves generated as you hand spin the wheels at about 1 revolution per second.
Note: The oscilliscope can detect problems that can't easily be found with a DMM (A scope pattern for a wheel speed sensor should show a classic sine wave alternating current pattern that changes both in frequency and amplitude with wheel speed. As the wheel is turned faster, signal frequency and amplitude should both increase. Damaged or missing teeth on the sensor ring will show up as flat spots or gaps in the sine wave pattern. A bent axle or hub will produce an undulating pattern that changes as the strength of the sensor signal changes with every revolution. If the scope pattern produced by the sensor is flattened (diminished amplitude) or is erratic, it usually indicates a weak signal caused by an excessively wide air gap between the tip of the sensor and its ring, or a buildup of metallic debris on the end of the sensor. A weak signal can also be caused by internal resistance in the sensor or its wiring circuit, or loose or corroded wiring connectors.)


INTERPRET DIODE-TEST RESULTS:
- If the DMM, in diode mode, reads infinity ("OL") in both directions, you've got a bad sensor or circuit
- If the DMM, in resistance mode, reads much greater than 7Mohms, you've got a bad sensor or circuit
- If all 4 sensors read OK, it's most likely the ABS control unit.
- If you think you found two bad sensors, you probably messed up.
- Rarely is the cause due to bad steering angle (yaw/lew) sensors
- Rarely is the cause due to a bad hydro unit
- The problem is almost always a wheel rotation sensor or the ABS control unit

ACTUAL RESULTS ON MY 2002 E39 THIS MEMORIAL DAY WEEKEND:


DOUBLECHECK WHEEL SENSORS AT THE WHEEL:
Note: You can run this test w/o removing the wheel but access to the sensor connector is easier with the wheels off the E39
- If one or more sensor circuits test bad in any of the three tests above ... then ...
- Locate the sensor blue connector in the rear of each front wheel well by turning the front wheels
- Easiest to first locate the sensor (bolted on the wheel carrier near the hub) and trace its wire back to a black plastic hinged box housing
- Open the locked hinged plastic rectangular black box with a small flathead screwdriver
- Locate the blue wheel sensor connector (next to a black brake wear sensor connector)
- Pull the blue wheel sensor connector out of the box and disconnect the two sides
- Re-check the sensor there with the diode function of the DMM



CHECK WHEEL SENSORS OFF THE VEHICLE:
- If any sensor still checks bad, pull the sensor off the vehicle for a closer inspection
- Chock wheels and jack E39 BMW and jack stand at the 4 jack pad locations
- Remove 4mm allen head bolts to sensor retention screw (two retaining bolts for fronts, 1 bolt for the rears)
- Pull wheel sensor out of hub assembly, straight up.
- Clean with CRC electronic cleaner
- Check with DMM diode-test meter as before
- Grease with Staburags NBU 12/K or equivalent grease
- Replace sensor back into hub assembly, snug tighten to 6 foot pounds
- Replace rear wheel, tighten to 82 to 96 foot pounds
Note: You might wish to swap sensors on the same axle when replacing so as to obtain further diagnostic information should an anomaly occur.
Note: Here is a picture of a dirty and cleaned sensor (magnetic particle buildup)



TEST BRAKE PRESSURE SENSOR (aka HYDRAULIC UNIT PRESSURE SENSOR):
- This test procedure kindly suggested by Max_VQ:
- Given 250 bar = 3,626 psi, and given 0-5 volts linear proportional output, 3,626 psi/ 5v = 725.2 psi/volt or 1.3 mV per psi.
- With the ignition on, measure the voltage on the pressure sensor while someone is pressing hard on the brake pedal
- My guess is that should create about 3,000 psi of force and should show around 4.13 volts.
- At rest it should show very close to 0 volts
Note: The front-brake pressure sensor provides a 0-5 volt linear voltage signal to the DSC III control module which is proportionate to how hard the driver is pressing on the brake pedal, from zero to 250 bars (3,626 psi), spanning (a) no braking, to (b) partial braking, and to (c) near-ABS-regulation state braking. This brake pressure sensor has three pins (a) power, (b) ground and (c) the 0-5 volt proportionate signal.
Note: By way of comparison, the Corvette also has a brake pressure sensor to indicate how hard the brakes are being applied; it monitors pressure from 0 to 2000psi generating a corresponding signal of 0.20 volts to 4.80 volts.

LOCATION OF FRONT-BRAKE PRESSURE SENSOR:
• DSC III 5.3 (740i/iL and 540i) - The brake pressure sensor is located in the charge pump assembly.
• DSC III 5.3 (750iL) - The sensor is located on the charge piston unit.
• DSC III 5.7 (ALL) - The sensor is located on the hydraulic unit on my 2002 E39.


TEST ROTATION RATE & LATERAL ACCELERATION SENSOR:
- We do not yet have a test for this sensor; a description of operation is all we have at the moment (please suggest a test procedure so all benefit)
- On Bosch DSC III (Bosch 5.7) the Rotation Rate sensor (yaw) and the Lateral Acceleration sensor have been combined into one unit located under the drivers seat under the carpet
- The degree of rotation rate (yaw) transducer outputs a reference signal of 2.5 volts and a linear voltage of 0.7 to 4.3 volts
- The lateral acceleration output signal should be 1.7 volts while the car is sitting still on a flat surface corresponding to 0 G side forces.
- The lateral acceleration transducer outputs a linear voltage of 0.5 to 4.5 volts corresponding to a G-Force range of -1.5 to +3.5 G side forces depending on the motion of a fixed capacitor plate relative to a floating capacitor plate.


TEST STEERING ANGLE SENSOR:
- We don't yet know how to test the steering-angle sensor (please advise)
Note: The steering angle sensor, mounted at the bottom of the steering column near the flexible coupling, utilizes two potentiometers to determine the steering angle and the rate of steering angle change, which are are the two raw signals the CAN bus microprocessor utilizes to create the steering angle signal for broadcast over the CAN bus. The DSC III logic compares the stored plausibility of the steering angle sensor against other DSC III inputs (front wheel speeds, rotation rate and lateral acceleration sensors).

STEERING ANGLE SENSOR:


REMOVE ABS MODULE:
- Remove the six T20 Torx screws holding the ABS module to the hydro unit
- Pull the ABS module straight out towards the passenger side headlight.
- Cover the hydro unit with aluminum foil to protect it from the elements
- You can drive the car but you won't have a speedometer or odometer
- Use a portable GPS unit with a speed display as your temporary speedometer
- You may not have cruise control (need to test this)
- Of course, you won't have ABS either but you didn't have that anyway

HINTS TO HELP OTHERS:
- Consider taking apart your ABS module and posting before rebuild and after rebuild pictures
- Consider paying rebuilders the extra $10 to return ABS modules that failed (so you can take it apart & post pictures)
- Consider selling your old module to the rebuilders if you buy a new or rebuilt ABS module from another vehicle
- A portable GPS unit doubles as a speedometer in the interim while your ABS module is being rebuilt

REINSTALL ABS MODULE:
- Note: There is a gasket attached to the new unit.
- Carefully place the new module over the control actuators.
- Loosely replace the six new T20 Torx screws included with the new module.
- Tighten snug tight, and then a little more to seat the gasket.
- Reposition the ABS electrical connector
- Press down on the ABS connector while pushing the retaining clip to the left
- Reassemble the Air Filter box & MAF (if it was disassembled for Torx access).

INITIALIZE ABS MODULES:

- Note: This step is only necessary if you installed an ABS module that wasn't originally in the car in the first place
- Take the E39 to an Indy to encode the VIN (I'm not sure what happens if you don't do this)
- Take the E39 to an Indy to check and adjust the steering angle (I'm not sure why)
- Some say the steering angle sensor may have to be recalibrated when you put on a remanufactured or new ABS module.

TORQUE TABLE:
- 4mm wheel sensor bolts (two each for the front sensors, 1 each for the rear sensors) = 6 foot pounds
- Combination lateral acceleration/rotational rate sensor (under driver seat) = 6 foot pounds
- DSC bolts to the hydraulic unit (new bolts only) = 26 inch pounds
- Hydraulic unit to body = 6 foot pounds
- Hydraulic unit mounting bracket = 6 foot pounds
- Brake lines to hydraulic unit = 13 foot pounds
- Wheel lug nuts = 82 to 96 foot pounds

DIAGRAM OF THE 2002 E39 DSC III BOSCH 5.7 SYSTEM:


USE THIS CHART TO DETERMINE WHICH ABS SYSTEM YOU HAVE:


Note: This ABS repair thread was compiled from scores of sources; special credit goes to many people, especially 540iman, BlackBMWs, Max_VQ, Edgy36-39, and others.
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#49 · (Edited)
You have done great work! And a lot of it, BTW!. You have a couple small let's say "inconsistencies". You do not need any alignment or other adjustment after doing a replacement unless you should find a "yaw" sensor as I call then is bad and this is seldom. If you need to replace a steering angle/yaw sensor, if you use diligent attention to get the new sensor angled at very close to the orientation of the old sensor, you are fine.

The biggest part to any DSC repair is diagnosis. Things can lead you in the wrong direction such as the three lights coming on and the speedo failing for instance. I believe more that one type of fault or bad sensor may cause the speedo to go out. We have a member I am working with now on this very problem. For me, my problem was the three light on and no speedo. It was my front right sensor. So, I believe the very, very first step should always be to test each sensor at the module connector. This way you also can see if the connection for the sensor is bad as well as the sensor itself. We are talking ABS senor/Wheel speed sensor here. The terms are used interchangeably. There is one on each wheel.. You must test each one at the module end of the cable to see what the module is seeing from each sensor. There are two ways to test, but I believe the diode test is more positive. A diode, almost by definition, conducts electricity only in one direction if it it working properly. A diode has polarity and only conducts one way. This is how they turn AC into DC. AC is always flowing current in both directions. DC flows only from positive to negative. It blocks that AC sine wave from flowing backwards so ac attached to a diode becomes 1/2 wave DC. It flows one way only. The wheel speed sensor has a diode action and to test it it should only conduct in one direction. Using a volt-ohm meter (VOM) with a diode check capability will show a good wheel sensor as "Open" in one direction" and a 1.75 volt drop in the other direction. By testing each sensor, you can take the guesswork out of it. If you use the resistance capability of the VOM to test a sensor, you should get around 3.3 Mega ohms in one direction and reversing the VOM test leads will yield approximately twice that first reading or say 7 mega ohms. You must be careful when doing it this way to not touch your fingers to the VOM probes or it is possible if your hands are sweaty to accidentally be measuring your body resisteance! That is why I chose the diode test method. If you find a sensor that is open or shows no voltage drop when checked in either direction, you have a bad sensor CIRCUIT. I say circuit and not sensor as we have not verified that we do not have a bad connection somewhere between the ABS module connector and the sensor itself. You have found potentially why you have the three lights, but the sensor could still be good and just have a badly corroded connection. You must check the sensor itself at the end of its pigtail to be sure. You can swap front sensors left to right or rear sensors left to right and if the nature of the error changes you have verified you have a sensor issue and not a module issue. Most sensors use the same 4mm Allen bolts to hold them in.

p.s. BlueBee, please send me your email address. Mine is wmliedtke@gmail.com I will send you the pictures I took. I could not get good closeups with the wife's good dital camera. It would not stay in focus. If you look at the underside of the connector, it is blue and has very tiny numbers at the sides. You can figure out what pin number is where. There are three rows of pins. You will need a small paper clip to get into the connector and not damage it.
 
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