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

Originally Posted by bluebee

Everything you need to know about opening & closing the ABS control module is here:
- Bill's ABS autopsy thread




Actually it's not new at all.

The diagnostic technique is already discussed ad infinitum in this thread (dental pick, toothpick, etc.).

These are the wires most often implicated:




It's intermittent for many of us.
There's not much diagnostic value in the intermittence in and of itself.
Quick99Si gave a great explanation of why above.



You're not the first person to say that but it perplexes me to hear that because I typed /pressure sensor in the bestlinks and I found this in less than a second or two:
- How to run a ABS BRAKE DSC trifecta brake pressure sensor diagnostic test (1)





I echo what Quick99Si said about the diagnostic tools.

See also this thread:
- The most often recommended BMW diagnostic tools & cable interfaces (1)



Here's Quick99Si's explanation:
- Why the 5-minute ABS DIY quick test doesn't always work, especially on brand new non-OEM wheel speed sensors (1)



My 30-year old Fluke 75 worked perfectly:


Here are my results using that DMM:


PS: I apologize that all the information above is already in this thread; these are all repeat questions which are already answered in this thread ... so I gave the same answers given before in this thread.

Great...thanks. Just to clarify, my trifecta lights are always on regardless of a cold or warm engine,...it's my speedo and cruise that work intermittingly.

Originally Posted by Big Chaze

it's my speedo and cruise that work intermittingly.

Oh. OK. My mistake.

I had misinterpreted the intermittence to be the ABS/BRAKE/DSC trifecta lights ... and not the actual gauge and stalk operation.

The speedometer is innervated by the left rear wheel speed sensor and the cruise control by the right rear wheel speed sensor ... so ... I'd suggest you run the ten-minute DMM test to compare those to what you get at the front sensors.

It would be rare for 'both' rear wheel speed sensors to go bad at the same time - but if they were, swapping them might not show any difference (if they're both bad).

Still ... the hour spent might be worth the effort after you do the ten-minute DMM test.

PS: You don't need to quote my whole post, with pictures, as it makes it hard to read for the user. I'd suggest you simply edit my quote down to the essential like I did with yours.

Originally Posted by bluebee

PS: You don't need to quote my whole post, with pictures, as it makes it hard to read for the user. I'd suggest you simply edit my quote down to the essential like I did with yours.

Youre the like the Forum God..

I will start doing research on the dmm test

Bavarian Technic says it's code 81 (Pressure Sensor Lead). If I can find a volunteer walking by saturday, I tried the DMM but since I live alone, it's too much. I am assuming the sensor is in fact bad. However, searching for a repair/replacement DIY for the pressure sensor seems to be as elusive as the pressure sensor threads initially were. I believe I know why me/others have had a hard time searching for pressure sensor threds (but no issues searching other topics). I believe because many of those postings are of pictures only (and the text is embedded in the picture), so there is nothing to search for a keyword (or at least very little). I've been googling and searching the forums, but have yet to find a DIY on pressure sensor replacement. I found two primitive links that give no DIY direction, including bleeding (or not) of the brakes. Anyone replace a brake pressure sensor on a 2002 e39 525i before?

The only two not so useful links I've found are:
http://tis.spaghetticoder.org/s/view.pl?1/06/55/93 and
http://tis.spaghetticoder.org/s/view.pl?1/07/64/36

So I just read this whole thread, my head is spinning, but i think i have found my problem. But just to be sure, let me share my symptoms and see what yall have to say. I am throwing a code 90, Intermittent system down. When driving any or all of the following may happen, usually they are set off by hitting any sort of bump in the road, like a bridge joint, but rarely, maybe never, happen when driving slowly over smooth pavement (happened twice in 5 miles of open highway but never in 45 minutes of <10mph traffic):
Engine failsafe prg, accompanied by the DSC, Brake, and ABS lights as well as a pulse of the brakes occur all at once, but it clears up after a half second and the car drives fine.
DSC light flashes even when not activated, like when driving straight on the highway not making any turns, accelerating or braking.
Brake light and ABS light on dash illuminate intermittently.
Radio head unit cuts out for 5-10 seconds.

So, are we thinking this is the ABS module? When I had the codes read no wheel speed sensor codes were stored.

I hate electrical gremlins...

...

Originally Posted by Pappa Bear

...usually they are set off by hitting any sort of bump in the road, like a bridge joint....

You may have a combination of things but when my ABS was triggered while slowly going over small but solid bumps (like the track for a sliding gate or in your case a bridge joint), it turned out to be warn or leaking thrust arm bushings. There are several DIY threads on that.

You described several other symptoms that aren't typically related to the thrust arm bushings but it might be a good place to start.

It's possible that could cause some extra wheelslip for a second but I would think the computer would have tolerances built in for that. I have aftermarket urethane bushings but they are getting kinda old. So yes they may need a checkup.

UPDATE: Not having much luck. The pressure sensor didn't fix it. Off to Boston tomorrow as is. Another let down. Of course in hind sight I'm kicking myself for not taking a chance/trying hard to shove DMM leads into back of pressure sensor connector and do the test, but the spongy inside was hard to penetrate and I didn't want to expose the inside of connector to future corosion. Plus I live alone and couldn't find anyone to help. So, so far, replaced ABS module that was never bad to begin with, and ATE never did say if defective, only that they bring it up to spec. And not the pressure sensor. Still get code 81 (sensor pressure). Actually mine says sensor pressure lead which is interesting if it was telling me a bad wire. But these are BMW/Bosch codes and my understanding it 81 is pressure sensor (period), no lead at the end. I tried resetting the code and it comes right back. I'll have to do more research but sounds like possible the pre-charge thing? But the symptoms described here that led me to replace sensor was that the pre-charge happened at or 30mph or so. My lights are on all the time. Although, before the module was rebuilt, the lights ONLY, and repeatable, came on after car was warm. Then while driving without the module, all three lights all the time, and the check engine light. Once I got the module back on, the check engine light went out within 10 miles of driving. Since then, they never go off-even when cold. AFter that, I bought the bavarian tech and it told me code 81. Now that is replaced $140 later (I did find one for $120), but it was not in stock and I was wanting it before I left for Boston.

Also interesting was that while unscrewing the sensor, there was zero, and I mean zero fluid that came out of the DSC unit. Another posting http://www.xoutpost.com/bmw-sav-foru...placement.html mentioned very little, but I got zero. The old sensor was slightly wet, but that was it. I did not bleed as a few others have/have not. And since I got zero fluid coming out, quickly put the new one one. Brakes are fine, but all three lights still. :-(

For FYI, I used a 15/16" deep socket. I tightened till it stopped and then a hair more. It's not like a spark plug where you keep going, this I could tell it was time to stop. You could easily use an adjustable wrench. It comes off with little force. The new sensor is the last pic (shiny one).

But alas, no fix for me. On the bright side, I have an expensive paperweight (the original, but working pressure sensor). :-)

Could the module that was rebuilt be sending a bad code (ATE from ebay)? Has anyone had a module rebuilt that was bad? How did you find out? I have heard units with 002 (mine) were problematic, but I would have thought ATE would have told me if there was an issue?

While prepping car for my trip to Boston, checking and filling fluids, I noticed some wetness under the what I think is the precharge pump. While it's possible fluid came out when I took the sensor out, I'm 99.99% certain none did. I watched very closely. However, it is possible that while the deep socket was on, adn while tightening, some came out and I missed it. It's also possible that it was runoff from filling up the washer fluid the otehr day (but doubt it as it would have dried up by now). It's also possible the unit is leaking. Aside from the precharge symptoms of failure I read about driving around 30mph (which I'm not experiencing), I heard someone say that if you slam on your brakes and car responds immediately (like stopping for a deer), it's not the pre-charge. I'm not a mechanic so not sure about that. However, about a week ago, someone cut in front of me and I had to hit the brakes VERY hard to avoid an accident. There was smoke (from one of the tires--maybe more), but the car stopped VERY good considering no anti-lock. And while I didn't go to that extreme tonight, the brakes work awesome. Since I've already thrown money at two parts that were not broken to begin with, I hate to replace the pre-charge too, but running out of things to replace. lol.

The pics arent' great. It's from my phone, upside down, and hard to get it in there. The last two pics are the closest but in person is more revealing. The wetness could also be from a deal bleeding the brakes, but doubt it as I don't think they'd go near there. I'm guessing there's a minor leak under precharge, but that I do not think would explain the code 81. Nor that the reservoir is 100% full. Actually, overfill--thank you dealer for the flush and overfilling it. :-)

Originally Posted by bluebee

Yes. Around post #48, I said it was bad because I "thought" it was bad because a diagnostic tool reported that as the symptoms.

But it was good. I never tested it. Bill, who really was the genius that got the testing suite all figured out, convinced me that all the diagnostic tools were reporting symptoms but that none of the diagnostic tools could report the problem (because of the way they're hooked up).

At another point, later in the thread IIRC, I got a DIFFERENT errant reading (of a bad wheel speed sensor) from the diagnostic tools. This time I knew it was bogus because I had already tested all four wheel speed sensors and knew they were good.

In fact, even after I had my ABS control module rebuilt by ATE, I still failed smog inspection a couple days later because there was still an errant P0500 wheel speed sensor malfunction listed as a pending DTC (which needed to be cleared).

But, all the diagnostic tools in the world will fail you in this particular situation. All this is said in subsequent posts of this thread so I'm repeating myself.

This is a (quick) summary of what the diagnostic tree "we" (tribally) recommend:
If you have the amber trifecta (BRAKE + DSC + ABS)...

• A. Test (with a DMM in the engine bay) the four wheel speed sensors ...
• B. If one wheel speed sensor is bad, test that one at the wheel (if more than one show up as bad, your technique is likely suspect) ... and if that one still tests bad, clean it ... and if it still tests bad, replace it.
• C. Otherwise, rebuild the ABS control module (generally one steel power wire lifts off its gold bondpad but sometimes the gold signal wires flop over onto each other).

BTW, this "amber ABS BRAKE DSC trifecta diagnostic tree" is sooooo simple, ironically, it's the reason it took me a year to believe in it (even though it was told to me in the beginning). I just couldn't believe it was that simple - I kept looking for a diagnostic aid to locate 'the culprit'.

Hi Bluebee,

I'm quoting you, because even though I read this post, and countless others, I still felt the urge to replace something based upon a tool. I'll be going back to square one and testing speed sensors, wires, etc even though I'm not getting a speed sensor code. Since replacing parts, including the abs module didn't help. But figure I (via your post) can save the next new guy from running out and replacing things. :-)

I probably would still have bought the pressure sensor because I live alone and had no way to test it on my own anyway. Still sux wasting money you could use for something else (like the DISA I need). :-) It's overwhelming as a new DIY'er. Tons of forums (here and elsewhere) from years ago to present with suggestions, then folks replying to posts with different or varying suggestions, and do / don't do that, and don't buy software, use free, etc. Even then, that diag forum is extremely overwhelming with link after link of do this, but not that before this, etc. and need to learn German. Someone like me tries the easy way by buying a program, but it should work. It's frustrating because I've been able to do the repeatable process things like oil change, diff change, spark plugs, O2 sensors, clean ICV, check DISA, etc. yet can fix the ABS trifecta lights--even after replacing the pressure sensor and the most common, the ABS module itself. igrumba.

Im gonna have to give this some more thought (no, not dumping the bimmer--lol). But I had the car for 2 months with zero brake issues. Had the brakes inspected before a prior trip to boston They said fine and did nothign to it. drove all way to boston and then some, return trip (3k miles). Still no ABS trifecta. About 2 weeks after that, bam they are on. I never noticed if my speedo stopped working (and don't think it ever did), but I did notice a few times that the auto door lock wasn't working (which hinted at a wheel sensor). But that never resurfaced. Perhaps my cleaning the sensors helped, I don't know. And the lights would always always go out when cold (3 plus hours sitting or so). I had no luck with DMM testing the speed sensors, like a few others here. Assuming the worst, I sent the module out for rebuild to ATE. I drove the car for 10 days while waiting for it. No issues, other than what others have reported such as no speedo, cruise, fuel gauge, and CEL being on. Brakes were normal other than no ABS functionality. Got the module back, CEL light went out but other three lights stayed on. And since new module light NEVER go out. I bought Bavarian Tecnic, got only code 81 (that's it), and replace pressure sensor. Still no go. Others' have suggested precharge pump, but I wasn't getting those symptoms, nor a precharge pump code.

Has all the above ruled out starting over? Or should I try retesting all the wheel sensors again, test pressure sensor (even though it's now brand new), etc.?

Bluebee. In post #48, you show 3 wheel speed sensor pics near the bottom of that post. One by the rotor, and the other two side by side. The top pic looks like my sensor, but the bottom two do not. It shows lots of magnetic dust. I didn't notice that before. Did you remove a plastic cap off the sensor? if so, I did not do that and only sprayed the outside of the sensors.

Did you use any of the BMW diagnostic tools like INPA or DIS? These seem to be what most people use to diagnose their cars.

Did you have your module rebuilt or did you buy a rebuild? It could be that you need to code it to your car. I installed a new module and all 3 lights stayed on. I had to code it to the car before it worked. There were several steps and I still don't know exactly how I did it.

From Bavarian support...

The description for this fault code from the original German is: "Druck Sensor Leitung." This translates Pressure Sensor Lead or Pressure Sensor Line. The tool does not indicate the problem is a faulty pressure sensor.

If you replaced the pressure sensor and the code would not clear it is because the pressure sensor itself is not the cause of the issue.

The Bavarian Technic tool works in the same way, and provides virtually the same information, as the BMW factory tool. Neither tool will typically yield fault codes that provide the exact cause of the problem, but typically point the knowledgeable mechanic in the right direction. We suggest you equip yourself with a factory service manual for your car to aid you in troubleshooting this issue.

Wow, it just keeps coming. lol. O2, plugs, ICV, need DISA, and really need CCV rebuild. And today I come out and the all yellow trifecta lights now show a red Brake light. and a cluster message that I can't read because of my pixel problem. lol. Does anyone know what the message is taht I can't read? Maybe there is enough of the message you know what it is. :-) But odd that it wasn't there yesterday. All I did was park overnight, startup the car this morning and there it was.

CHECK BRAKE LININGS

http://www.bimmerfest.com/forums/sho...d.php?t=536513

Your pads are worn down or the sensor wire is grounded for some other reason... or you have an electrical gremlin causing all kinds of issues.

Red brake light is often used to denote low brake fluid, but in your situation, it's likely related to your pads. Gonna have to do your research on this one. Maybe it is in fact low fluid caused by worm pads?

Originally Posted by Quick99Si

CHECK BRAKE LININGS

http://www.bimmerfest.com/forums/sho...d.php?t=536513

Your pads are worn down or the sensor wire is grounded for some other reason... or you have an electrical gremlin causing all kinds of issues.

Red brake light is often used to denote low brake fluid, but in your situation, it's likely related to your pads. Gonna have to do your research on this one. Maybe it is in fact low fluid caused by worm pads?

This....
And, check ebrake and brake switch, even brake lamps depending on model and year.

Originally Posted by Big Chaze

This....
And, check ebrake and brake switch, even brake lamps depending on model and year.

Good points. I'll have to research how to check the emer brake, but that brings up what might have changed overnight. I always used the EMER brake when parking. A carryover from my dad telling me when a kid to use it to save the trainy. I'll also have to look up how to check the brake switch for 2002 e39 525i. I will check the lamps asap.

However, I do think it's just that I need new rear brakes. Around december, I had the brake shop check all the brakes for me, before going on my first Boston trip. They said all was ok, but front needed soon and rear had 50%. When I got back I had the front brakes done. Fast forward to this week, I went to Boston again (on same 50% pads). Maybe that 50% was a guess? Anyway, I do'nt have a micrometer, but the rear pads are approx 4mm while front look close to 10mm (at least 8mm). The rear rotors were a little thinner than the fronts, but according to what I read on a bluebee post, the rears are slightly thinner, or at least should be a minimum of .720 or something like that. Again, without a micrometer, I have no idea if rotors need replacing. But the pads being at 4mm, and bluebee's chart saying minimum is 3mm, I'm guessing that is enough to set of the brake pad sensor? I would say the front rotors are approx 1mm, maybe 1.5mm thicker than the rears (which pads have approx 4mm left too).

If so, it looks like my yellow brake light going to red was just a coincidence to my ABS issues. :-)

The money pit. :-)

Priorities? DISA, CCV, or brakes? I know, All are needed asap.

I was able to do the DMM test from the ABS module connector, where I previously was unable to. I do believe the multimeter I had was the issue. While it had good batteries, it took the kind with 3 button cells (either 1.1V each or 1.3V each). Diodes have a forward and reverse voltage and I think the button cells weren't good enough to test the circuit (wheel sensors). So I got a 9V DMM at menards and was able to test, although it was not conclusive (only one was slightly off). three of the four sensors/tests were 1.9V one way, and 0L the other. the right rear was 1.8V and 0L. Similary, and very interesting, resistance was high. 18Megaohms one way and 8M the other way. The right rear was 17M and 8M.

I think I'm going to take up ATE on sending unit back for another test. With wheels sensors testing ok, and BPS replaced as well as the ABS module, it's possible my "002" ABS module is the issue. who knows.

Hey guys,

I just got the AWD/DSC and yellow brake light on my 2006 530Xi. Any idea how much of the information in this thread is applicable to later models? I am thinking since I have both dsc and brake warnings that I may have a wheel sensor bad. I figure that would be an easy one to check out.

Any thoughts?

I was wondering,...Im running DIS/Inpa and both programs revealed I have 3 bad speed sensors. How likely is this? I mean, I have been ruinng the car with the trifecta for 2 years.

Originally Posted by munsonbw

Any idea how much of the information in this thread is applicable to later models?

Many known BMW faults transcend vehicle lines.

Notice that more than just the E39, for example, has the problematic Bosch 5.7 ABS control module.

Originally Posted by Big Chaze

both programs revealed I have 3 bad speed sensors. How likely is this?

Most here would say you are reading what the (probably broken) ABS control module is 'thinking' since you are probably NOT isolating the sensors during those tests.

So, without isolation, all the fancy schmancy tools can read is what the computer thinks is going on.

I suspect you have the 7th wire lifted inside the ABS control module. You can open it up to find out for sure.

Most here would say you are reading what the (probably broken) ABS control module is 'thinking' since you are probably NOT isolating the sensors during those tests.

So, without isolation, all the fancy schmancy tools can read is what the computer thinks is going on.

I suspect you have the 7th wire lifted inside the ABS control module. You can open it up to find out for sure.[/QUOTE]

I tested both front sensors at the abs connector under the hood and for the life of me couldnt get my mm to read anything other than zero..Just figured it was impossible for both sensors to be reading open circuit....but dis has led me to believe otherwise..
Damn! What to do??

Originally Posted by bluebee

Most here would say you are reading what the (probably broken) ABS control module is 'thinking' since you are probably NOT isolating the sensors during those tests.

So, without isolation, all the fancy schmancy tools can read is what the computer thinks is going on.

I suspect you have the 7th wire lifted inside the ABS control module. You can open it up to find out for sure.

..

I tested both front sensors at the abs connector under the hood and for the life of me couldnt get my mm to read anything other than zero..Just figured it was impossible for both sensors to be reading open circuit....but dis has led me to believe otherwise..
Damn! What to do??

Originally Posted by Big Chaze

Damn! What to do??

During this thread, many people had errant zero readings on the wheel speed sensors. So far, IIRC, they all figured out what the problem was (usually the meter or the technique, e.g., too large a wire).

Anyway, you can test the sensors closer to the wheel (just disconnect the sensor at the box in the wheel well which is explained in post #48 of this thread).

Also remember there 'are' six other tests you can run on the sensors (although none is as easy as the DMM test). For example, you can check running voltage pulses as you spin the wheel (as explained in post #48 of this thread).

And, you 'could' buy one (not more than one) sensor to install and test it; but most would say that's a waste of money.

And, you could open up the ABS control module to probe the seventh silvered wire to see if it lifted off its bondpad.

Or, you could send your ABS control module out to one of the three recommended rebuilders for testing & repair.