Is it possible for the diagnostic tools to diagnose the ABS BRAKE DSC/ASC trifecta? - Bimmerfest - BMW Forums



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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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Old 04-11-2015, 03:20 AM
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Is it possible for the diagnostic tools to diagnose the ABS BRAKE DSC/ASC trifecta?

Is it even possible for the diagnostic tools (such as INPA, DIS, Carsoft, PASoft, etc.) which connect to the OBD or Pacman ports, to correctly diagnose the ABS BRAKE DSC/ASC trifecta?

Everyone wants the diagnostic tools to help them diagnose the ABS BRAKE DSC/ASC trifecta, yet, there is a valid argument by some that they can't, simply because they are connected in the wrong spot (and therefore can not possibly get the correct information, particularly from a bad ABS control module, the argument goes).

Looking to cross reference that post in the bestlinks, I noticed there wasn't yet a canonical thread listed for this topic.

Instead, there were a half dozen isolated posts to other threads:
- The many explanations by 540iman as to why the fancy schmancy diagnostic tools almost always fail to properly diagnose the trifecta or bifecta (1) (2) (3) (4) (5) (6) (7)

So, the main purpose of this new thread is simply to have a home for whether the standard INPA/Carsoft/DIS/etc. diagnostic tools can possibly correctly diagnose the ABS BRAKE DSC/ASC trifecta (and probably the bifecta).

Discussion is welcome as to whether or not it's possible for the fancy diagnostic tools to diagnose the trifecta when connected to the OBD or Pacman ports.

See also:
- How to diagnose the BMW ABS BRAKE DSC/ASC trifecta (1) & why the 5-minute ABS DIY quick test doesn't always work, especially on brand new non-OEM wheel speed sensors, by Quick99Si (1)
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Last edited by bluebee; 04-11-2015 at 08:12 AM.
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Old 04-11-2015, 03:34 AM
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Here are a half-dozen separate arguments by 540iman (over the years) that the problem with diagnosing the trifecta from the obd/pacman ports is that the tools can't get the information they need from those locations...

> E39 (1997 - 2003) > ABS/DSC/Brake Lights
Quote:
Originally Posted by 540iman View Post
Someone said they don't believe you can diagnose a bad module. You can. You just can't tell a bad input from a bad module. You can diagnose a faulty module that won't communicate with the other modules/DMS for example. Just not a bad sensor from a bad module.
> E39 (1997 - 2003) > 2002 E39 ASC BRAKE ABS lights on => Diagnostic Procedure & Parts Location
Quote:
Originally Posted by 540iman View Post
... The dealer's scan tool, Carsoft, or whatever scanners see many different symptoms that they don't like.

Missing pulses, no pulses whatsoever, misshapen pulses as viewed on an oscilloscope, etc. They know what portion of the module they reside in. They can't tell the mechanic the cause, only the symptom.

So, they identify the portion of the module that is whacked AT THAT MOMENT IN TIME.

If the car were on a dyno and the wheels spinning, it would be better, but still not absolute because then it would possibly know if it is seeing pulses that the wiring is ok, but the sensor itself LIKELY bad. My Carsoft told me on my realtor's car that his sensor wiring was at fault when he actually had a bad sensor itself.

I have no clue how it thought it could be so specific as to identify the wiring and not the sensor, but that is what it said. The same software, on my car, said it was the sensor itself-and it was after I confirmed by disconnecting and checking sensor with the VOM.

I am not discounting that the scanners can diagnose some faults (like communication faults) 100%. They can properly identify defective modules in many cases-say when a module is pulling no current whatsoever.

Only the module can cause a symptom such as this. When it gets to the speed sensors themselves, they can be right still, but at a smaller percentage because of the nature of how the sensors generally fail. MOST (not all) go open.

The cheaper scanners such as Carsoft assume the module itself works as long as it has communication. If a channel is dead, it will always diagnose as a bad sensor or sensor wiring. It will not return a bad I/O transistor in the module correctly. It will not diagnose a bad solder connection in the module as such. It will deliver a bad sensor message 100% unless the solder connection is not in the speed sensor signal path (again, like a communication error caused by a bad solder connection)-that it will get right.

Talk to your Stealership tech. and they will tell you. Mark (aka EAC tuning Mark) has software very similar to what the stealer has and while he is working many of the bugs out of it, he will tell you that there is a big difference between accurately diagnosing the symptom and the actual cause. That can be trial and error. Many here will tell you of countless sensors diagnosed and replaced on to ultimately find it is the module itself.

I don't know if I clarified for you to your satisfaction. I can only tell you what is and why I as an electronic tech can justify it. Just do not believe that all bad sensor diagnosis are correct. People have spent countless dollars chasing supposedly bad sensors read by GT-1s down to Peakes.
> E39 (1997 - 2003) > 2002 E39 ASC BRAKE ABS lights on => Diagnostic Procedure & Parts Location
Quote:
Originally Posted by 540iman View Post
... I think that a lot of the problem is that Carsoft and others don't, as you say tell you that the patient has a low white blood cell count and stop there.

They often "attempt" to go farther and diagnose the patient as having cancer.

The last ABS system I repaired was interesting because all I have in the way of BMW-specific diagnostic equipment is Carsoft. The buddy I was working with had INPA, progman, and all the other stuff you mentioned. Both our diagnostics lead to a faulty yaw sensor and NEITHER were correct.

Carsoft also said a wheel speed sensor was bad which also was wrong. I determined it was wrong with a diode test. I don't agree with your statement that the diode or resistance test is not conclusive.

If you test at the module connector, it is less conclusive then if you remove the suspect wheel sensor-have it and it alone in your hand and then test it with a VOM. You need to make sure that the sensor does not have metal shavings stuck to the end of the sensor and that the wiring to the sensor (between the module and each sensor) is not also what is giving you an open or short.

I think what was being conveyed to Agent15 is to not be surprised if the diagnosis, as given by some equipment, will be wrong and may lead to replacement of parts and the problem will still be there.

You must, as you say, get more tests that will further define the problem. Initially, I think I was of the opinion that 90% of the time, problems with the trifecta lights will ultimately be a bad module and 10% a bad sensor. I now think it is more like 70-30.

I have found more bad sensors lately, but have NEVER found one that tested bad and was really good or vice verse. I would bet a paycheck that if Agent15 or anyone for that matter has the sensor in his hand and can get meter leads deep into the sensor such that he can test either in ohms or voltage bias forward and reverse (diode test) and the sensor tests bad, that it IS bad. Conversely, if it tests "ok" meaning there is a definite difference when meter leads are reversed and sensor does not test open or shorted BOTH ways- it is NOT the fault.

The main point is that any diagnostic equipment that does not test by going between the sensors and the module simply can not definitively see a bad module from a bad sensor.

It is as simple as stating that a blood pressure cuff can not diagnose whether high blood pressure reading at a cuff is because of a faulty heart or a clotted artery. You must somehow get readings I suspect (certainly not a Dr.!) between the heart valves or whatever you do to isolate. If your Indy or dealer hooks up to your OBDII port or your 20 pin and definitively tells you that you have a bad wheel speed sensor, that person is full of doo-doo.

Only thing you can diagnose correctly 100% of the time from either of these two points is a bad module due to a communication error or similar. They can not tell a bad input (sensor) from a bad module at these test points.
> E39 (1997 - 2003) > 2002 E39 ASC BRAKE ABS lights on => Diagnostic Procedure & Parts Location
Quote:
Originally Posted by 540iman View Post
Bee, you wanna tell him or you want me to? Faulty pressure sensor indication can be another one of those input sensor errors that end up really being the module.

You need to back-probe pressure sensor to see what your output is with no pedal pressure and then with pedal pushed hard.

It might be your sensor, but just like any other input to the module, unless you physically test that sensor don't be surprised if your error remains. Bad pressure sensors are very uncommon.
> E39 (1997 - 2003) > ABS trifecta fixed
Quote:
Originally Posted by 540iman View Post
I have said this so many times that I am actually sick of hearing myself, but it is so important that when diagnosing the trifecta that it is also a process of thinking through what readings, errors, et al. when you test.

Remember that all speed sensors pass through the ABS module before any possible connection to ANY OBD port.

When you are seeing MULTIPLE speed sensor errors all at once, what is in common between them? The MODULE.

If channels of the module are open, then all the sensors that go through that channel will also *appear* open.

Chances of three sensors bad at once? Not a chance.

But the module touches them all. This is why it is critical that to truly test a wheel speed sensor whether you use diode, resistance, or a scope that you must break the circuit at the module by disconnecting the multi-pin connector so it is just your testing device and the sensors.

One exception that will clearly show on any decent scan tool plugged in at the OBD port would be when there is a communication fault between the ABS module and the Bus. This error ain't kosher ever. bad speed sensors??

Maybe one, more than one I'm not buying it if all was well before.
> E39 (1997 - 2003) > 2002 E39 ASC BRAKE ABS lights on => Diagnostic Procedure & Parts Location
Quote:
Originally Posted by 540iman View Post
...we are telling you the experiences we have encountered to try and help others who face the same thing, as well as explain- as best we can- possible reasons for the inability of every diagnostic device that I know of personally having misdiagnosed this error "area"....the trifecta brake lights.

No subject likely has as much coverage as it is very frustrating for the average DIY'er, which after all is what brings most of us here, to diagnose using all the standard devices available to not just us, but to indys and techs we have gone to for help.
> E39 (1997 - 2003) > ABS Trifecta lights- how I would approach
Quote:
Originally Posted by 540iman View Post
... hooked up Carsoft and Carsoft says my LR speed sensor CABLE is bad.

How it distinguished between the cable and the sensor I don't know. I will assume it saw the circuit as "open"- could be the opposite too and it saw a dead short. However, when sensor is bad, they will often read open both ways.

I checked with my VOM in diode position at the Module end of cable (connector). Tested between 13-29 iirc and showed 50 ohms in both directions. Checked a different speed sensor and it read a correct "open" in one direction and 1.707V in the other direction so I knew I really did have a sensor problem. I unplugged the sensor at the LR wheel and measured at the end of the speed sensor pigtail and guess what...it read the same...basically a "soft" short (50 ohms) in both directions at the sensor. I have one on order.This is in my estimation the correct way to try and separate the sensor from a module issue. Had that sensor read open in one direction and 1.7V in the other, I would be seeing if the module was still under warranty. Some have said they don't have a meter with a diode check position or that their meter gives different readings from my Fluke 85. In my opinion, it does not matter. Test all four sensors and it does not matter whether you use the resistance setting (use mega ohms setting) or a diode setting, don't sweat getting readings identical to mine.Look for one senor of the four that reads DIFFERENT from the others and then double and triple check that your paper clips or whatever you are using to insert into the connector are absolutely making good connection.

Also, you must test each sensor twice. Once with positive lead of your meter and black or negative lead from you VOM oriented one direction and then reverse the meter leads to the same two pins.

You want to check the sensor forward biased and reverse biased. If the readings are the same, your sensor is toast. Three of my four sensors checked fine. One was a bastard child! Hope this helps someone. Nothing here is new. You will find all this same information in BlueBee's comprehensive post. I just walked you through how my mind thinks on this issue.
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  #3  
Old 04-11-2015, 03:38 AM
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The issue with using diagnostic tool for diagnosing the trifecta is that the scanner can't tell if it's a bad module or bad sensor. If it's a bad sensor diagnostic tool can correctly diagnose it. When my wheel speed sensor failed I used INPA, which told me it was bad wheel speed sensor. I also verified the diagnose with a multimeter.
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Old 04-11-2015, 03:46 AM
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Quote:
Originally Posted by HTK12 View Post
The issue with using diagnostic tool for diagnosing the trifecta is that the scanner can't tell if it's a bad module or bad sensor.

If it's a bad sensor, the diagnostic tool can correctly diagnose it.

When my wheel speed sensor failed I used INPA, which told me it was bad wheel speed sensor. I also verified the diagnose with a multimeter.
Personally, I'm very confused if this is ALWAYS the case, or not.
There is a very detailed thread by Quick99si on this topic of testing the sensors using the fancy tools (he had a non-oem wheel speed sensor turn out to be bad, but which tested good on the DMM quick test).

Most of his details were beyond my comprehension (see the thread tidbits below); but what I garnered out of it was something like this:
1. If the ABS control module is good, the fancy tools can correctly diagnose a bad wheel speed sensor; but,
2. If the ABS control module is bad, then the fancy tools can't even diagnose a bad wheel speed sensor correctly.

Can someone else read the Quick99Si thread and summarize for us?
> E39 (1997 - 2003) > My experience with the trifecta lights (ABS/DSC/Brake)

Quote:
Originally Posted by Quick99Si View Post
...
Parting words: my advice is to datalog the wheel speed sensors! Go to your indy, find a local member, or get your own setup [urlhttps://www.bimmerfest.com/forums/showthread.php?t=561237=]with info found here[/url].

If you can't communicate with ABS/DSC, odds are your module is toast; if you can, find the oddball reading and work on it by inspecting the wiring and/or swapping sensors side to side.

Adi
Quote:
Originally Posted by Quick99Si View Post
First post above updated with

24 wrong impulsering
Error frequency : 219
Vehicle speed 49.19 km/h
-------------------------------------------------------------
6 wheel speed sensor front right plausibility
Error frequency : 255
Vehicle speed 11.38 km/h
Quote:
Originally Posted by bluebee View Post
Oh my!

This is a great thread showing that there 'is' value in the 'fancy schmancy' diagnostic tools when used well!
Note: JeffStri will be ecstatic!

Now, if only we can hone the BMW dealer-diagnostic procedure to make it as easy as we can possibly make it for newbies to follow at home WITHOUT screwing things up (i.e., diagnostics only ... not coding or programming).

BTW, if you do suspect the (brand new) wheel speed sensor is bad, it would be very helpful if you can attempt to run any of the five other known direct tests of the wheel speed sensors to see what readings you get!
Quote:
Originally Posted by Quick99Si View Post
I will retest the bad speed sensor. My results from initial testing are posted above, and it really looks like it tested fine. My bad speed sensor is *intermittently* bad in practice, however... it seems to work fine up until 10-20km/h and then it sort of cuts in and out.

I actually have video of this happening, showing the DIS live logging screen as I accelerate and drive at a steady speed.

It's worth noting that the bad sensor is a non-OEM unit, branded something like TEAK-E, while the good one has Mayle all over it along with "Made in Germany
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Old 04-11-2015, 03:48 AM
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BTW, a common bogus error that pops up when the ABS control module is removed or bad is the P0500/P0501...
-What's this about the P0500 setting the SES (1) & why you want to wait a week before getting a smog test after removing your ABS control module (1)
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Old 04-11-2015, 03:51 AM
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Another common bogus error that pops up because the fancy diagnostic tools are connected in the wrong place is the error 81 brake pressure sensor (I had this one myself)...
- How to properly test the BPS brake pressure sensor (1)
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Old 04-11-2015, 03:54 AM
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Yet another common, always bogus error is the implication of the extremely expensive hydraulic pump which many people get from their indy (who doesn't realize the tools fail to diagnose this problem properly due to the location of their connections)...
- Why your trifecta is probably not the ABS hydraulic pump failing (1)
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Old 04-11-2015, 03:56 AM
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Another very common error (again, probably bogus, but I'm not sure as I never had it myself) is the implication by the fancy diagnostic tools of the steering angle sensor ...
- How to properly test and replace the steering angle sensor (1)
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Old 04-11-2015, 07:43 AM
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Quote:
Originally Posted by bluebee View Post
Personally, I'm very confused if this is ALWAYS the case, or not.
There is a very detailed thread by Quick99si on this topic of testing the sensors using the fancy tools (he had a non-oem wheel speed sensor turn out to be bad, but which tested good on the DMM quick test).
As I said using diagnostic tool is useful only when the module is good. What I do is first read the codes with INPA. If I get error code telling me I got bad wheel speed sensor I check it with a multimeter. If the diode test also shows the sensor bad it means you got a bad wheel speed sensor or wiring issue. You can check the wiring by removing the connector from the suspected wheel speed sensor and shorting the the connector and then checking for resistance (don't short the wiring before removing the connector from the module). Only replace it with a sensor that is manufactured by a good manufacturer. OEM is Siemens/VDO. When my wheel speed sensor failed I replaced it with Bosch. Bosch shoud know how to make a wheel speed sensor because they made the ABS module.

If the multimeter shows the sensor as good you can use live-data to see is that wheel speed sensor showing the same speed as the rest of them. I diagnosed one case where there was no codes/lights but the ABS was cutting in even on dry asphalt. Using live-data it was quite obvious that one sensor was giving false speed reading. When these modules fail you usually get the bad wheel speed sensor error because the module can't get any reading from the sensor.

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Old 04-11-2015, 04:16 PM
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Quote:
Originally Posted by HTK12 View Post
...using a diagnostic tool is useful only when the module is good... When these modules fail you usually get the bad wheel speed sensor error because the module can't get any reading from the sensor.
This is an important distinction, which, if true (and I don't doubt it), immediately begs two questions...
  1. When INPA reports something as bad, how do you know that INPA is right, or that INPA is wrong?
    • Is INPA right (because the ABS control module is telling it the right thing)?, or
    • Is INPA wrong (because the ABS control module is telling it the wrong thing)?
  2. What are the "things" that INPA can get right when it's right?
    • Can it diagnose bad wheel speed sensors? (probably)
    • What about brake pressure sensor (which, to date, have all been bogus reports)
    • How about the steering angle sensor?
    • Or, the hydraulic module (which has been bogus in all reports I know of, to date)
    • ? what else ?
Quote:
Originally Posted by HTK12 View Post
What I do is...
Since people will be following this thread for diagnostic advice, how does this sound for a step-by-step diagnostic sequence (based off of what you said above)?
  1. Read the diagnostic error codes using INPA hooked to the OBD port (or to the Pacman connector for older E39s)
    • While you're at it, check INPA live-data results to see if the implicated wheel speed sensor is acting differently from the other three sensors.
  2. If INPA implicates a specific wheel speed sensor ...
    • Run the fifteen-minute DMM diode & resistance quick test on all four wheel speed sensors from the blue (or white for the older E39s) harness connector to see if that one sensor is "different".
  3. If the implicated WSS still tests "differently" than the other three
    • Optionally test at the wheel in order to isolate the wiring from the sensor itself
    • Do this by removing the connector from the suspected wheel speed sensor and shorting the the connector and then checking for resistance
    • (don't short the wiring before removing the connector from the module)
  4. If the implicated WSS still tests bad
    • Replace that one bad WSS with a known-good brand of WSS
    • OEM is Siemens/VDO, or use Bosch (who made the ABS control module)
    • If you're diagnosing more than one WSS as being bad, double check as something is likely awry with your diagnostic procedure.
How would you IMPROVE that sensor-testing procedure above to make full use of the live-test capabilities of INPA?
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Old 04-11-2015, 07:23 PM
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I tried diagnosing whether my thermostat was bad or not using DIS. I read the fault code, and began the troubleshooting procedure.

It prompted me to remove the connector from the thermostat, and then connect some type of adapter to the wiring harness from the t'stat. And that was the end of my diagnostic procedure using DIS.

The problem with using DIS on a virtual machine is that the rest of the GT1 DIS is missing, that is, the big honkin' rollaway that actual dealerships use.

I am not sure what the diagnostic procedure on DIS is for the ABS module. But it's a lot more than reading the fault code.
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Old 04-11-2015, 08:54 PM
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Originally Posted by TheHockeytowner View Post
.the rest of the GT1 DIS is missing, that is, the big honkin' rollaway that actual dealerships use.
That's a good point, as this photo shows...
- What are the most often recommended BMW diagnostic tools & cable interfaces (1)

Quote:
Originally Posted by TheHockeytowner View Post
It's a lot more than reading the fault code
I think, based on the input above, that it's even worse, in that the fault code isn't even correct when a faulty ABS control module is the one telling DIS what the code is.
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Old 04-12-2015, 04:45 AM
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Quote:
Originally Posted by bluebee View Post
This is an important distinction, which, if true (and I don't doubt it), immediately begs two questions...
  1. When INPA reports something as bad, how do you know that INPA is right, or that INPA is wrong?
    • INPA can be right (because the ABS control module is telling it the right thing), or
    • INPA could be wrong (because the ABS control module is telling it the wrong thing).
  2. What are the "things" that INPA can get right when it's right?
    • Can it diagnose bad wheel speed sensors? (probably)
    • What about brake pressure sensor (which, to date, have all been bogus reports)
    • How about the steering angle sensor?
    • Or, the hydraulic module (which has been bogus in all reports I know of, to date)
    • ? what else ?
  1. With INPA or any other capable scanner:
  2. Can it diagnose bad wheel speed sensors? If the module is good then yes, with a bad module no
  3. What about brake pressure sensor (which, to date, have all been bogus reports) you can check the value with live-data, but as you said that error usually means bad module
  4. How about the steering angle sensor? Yes you can check the current angle and calibrate, if needed.
  5. Or, the hydraulic module (which has been bogus in all reports I know of, to date) You can activate the hydralic pump (service function to bleed the ABS)
  6. ? what else ?

[/LIST]
Since people will be following this thread for diagnostic advice, how does this sound for a step-by-step diagnostic sequence (based off of what you said above)?
  1. Read the diagnostic error codes using INPA hooked to the OBD port (or to the Pacman connector for older E39s)
    • While you're at it, check INPA live-data results to see if the implicated wheel speed sensor is acting differently from the other three sensors.
  2. If INPA implicates a specific wheel speed sensor ...
    • Run the fifteen-minute DMM diode & resistance quick test on all four wheel speed sensors from the blue (or white for the older E39s) harness connector to see if that one sensor is "different".
  3. If the implicated WSS still tests "differently" than the other three
    • Optionally test at the wheel in order to isolate the wiring from the sensor itself
    • Do this by removing the connector from the suspected wheel speed sensor and shorting the the connector and then checking for resistance
    • (don't short the wiring before removing the connector from the module)
  4. If the implicated WSS still tests bad
    • Replace that one bad WSS with a known-good brand of WSS
    • OEM is Siemens/VDO, or use Bosch (who made the ABS control module)
    • If you're diagnosing more than one WSS as being bad, double check as something is likely awry with your diagnostic procedure.
How would you IMPROVE that sensor-testing procedure above to make full use of the live-test capabilities of INPA?[/QUOTE]

That list is pretty good just a note to 1. if you are using live-data to check the wheel speed sensor reading you need 2 persons, because the car needs to be moving at steady pace, while one is looking at the scanner and one is driving. I strongly advice against doing this alone. Driving the car without looking where your going is dangerous!

A bit clarification to 3.

Optionally test at the wheel in order to isolate the wiring from the sensor itself
To test the wiring from the module to the wheel speed sensor. Remove the connector from the suspected wheel speed sensor and short the two pins, then check resistance at the ABS module connector.
(don't short the wiring before removing the connector from the module)
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Old 04-12-2015, 06:17 AM
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540iman 540iman is offline
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If you want to quote me then you will see that I said there were some errors that a scan tool can get correct. I just picked one- a communication error- that a scan tool can get right. There are others such as "implausible" pulse patterns which show a pulse is getting through the module, but is just "not realistic" in the scheme of things. A bad steer angle "balance" is another. Full left turn should register 500 pulses and full right hand turn should also count close to 500 pulses to be "balanced". When turning wheel all the way in one direction and the module only sees say 460 pulses and turning wheel full in the other direction will yield 500 pulses PLUS whatever it was short in opposite direction (ie. 540 pulses). Steer angle does not always need calibration when module is replaced, but if alignment is getting further out or sensor itself has gotten knocked a little off. the module does not truly know when steering wheel is pointed straight which it must know in order to engage DSC properly in the case of a swerve or hitting patch of ice. DSC is simply an intelligent application of the proper brakes and control over the throttle body. The reason the ABS module needs the car's proper vin# is because the vin# conveys to the DSC system every option the car has. What engine, sedan or touring, speed sensitive steering, vehicle weight, etc. The module has a custom method of DSC or ASC depending on what vehicle is under that module. It only wants the vin just like real.oem needs it.... It needs to know facts about what it is to control,

Finally, a scanner CAN get the correct diagnosis of an ABS trifecta, but it can be fooled as well and the best way to use the scan tool is to let it read what it "thinks" the error is and then break the connection at the ABS and use a secondary check to confirm. Like the instance of the scan tool saying 3 speed sensors were bad.... break the connection and verify in another manner whether the speed sensors agree when read by another tool such as a multi-meter, a scope, or by switching sensors left to right or whatever to see if error now moves to another wheel. It has been my experience that as often as a scan tool is right, they also mis-diagnose an equal percentage. YMMV Using a quality tool such as a fluke meter, I have never been lead astray or bought parts I did not need. For me, this subject has too many "whiskers" on it and people can follow my advice or leave it- I really don't care. I am relaying what my experiences have been in the hopes that it may help someone as it helped me.
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Old 04-12-2015, 11:28 AM
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bluebee bluebee is offline
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Quote:
Originally Posted by 540iman View Post
If you want to quote me ...
It's very important to accurately quote you because you were the first one (that I know of anyway) to suggest the DMM quick test (way back in post #45 of the canonical trifecta thread).

Overall, I think we're getting a consistently inconsistent answer - which is a good thing ... (if a bit confusing)...
Quote:
Originally Posted by 540iman View Post
...a scanner CAN get the correct diagnosis of an ABS trifecta, but it can be fooled as well and the best way to use the scan tool is to let it read what it "thinks" the error is and then break the connection at the ABS and use a secondary check to confirm.
I don't trust a tool that tells me the correct thing half the time, and lies to me the other half - but - having said that - I can see the logic in your suggestion.

Is this the refined suggested diagnostic tree with, and without a scan tool?

If you have the trifecta but you don't have access to the scan tool, then the old school trifecta diagnostic method is:
  1. Test all four sensors at the harness connector.
    1. If one tests bad...
      • Re-test it at the wheel.
      • If it still tests bad, consider running any of the half-dozen additional tests.
      • If it still tests bad, replace it (with Siemens/VDO/Bosch only!).
    2. If more than one test bad...
      • Fix your technique (change DMM and/or probes)
      • Once fixed, go back to step 1.
    3. If none test bad...
      • Probe the 7th aluminum wire inside the ABS control module
      • If the wire is loose
        • Either re-attach the wire yourself (1), or,
        • Send the ABS control module out for repair (1), or,
        • Buy (& code) a used or new ABS control module (1).
      • If the wire is not loose
        • Go back to the diagnostic beginning.
However if you have both the trifecta and a scan tool, then, by all means, use the scan tool - but do not accept scan-tool output as gospel!
  1. WHEEL SPEED SENSOR:
    • If the scan tool implicates a wheel speed sensor, first take it seriously enough to independently test the wheel speed sensor (1).
      • With the help of a partner, test the live data output (at speed) from the implicated sensor
      • (We need to summarize the half-dozen additional tests that can be done on a wheel speed sensor that can be done with the diagnostic tools).
    • If the scan tool implicates multiple wheel speed sensors, strongly consider whether the ABS control module is telling the scan tool a fib (1).
  2. STEERING ANGLE SENSOR:
    • If the scan tool implicates a steering angle sensor, consider whether the ABS control module is telling the scan tool is telling a fib, by independently testing the steering angle sensors (1).
  3. BRAKE PRESSURE SENSOR:
    • If the scan tool implicates the brake pressure sensor, then almost certainly the ABS control module is telling the scan tool a fib (1).
  4. HYDRAULIC MODULE:
    • If the scan tool implicates the hydraulic module, then almost certainly the ABS control module is telling the scan tool a fib.
  5. ? Did I miss a commonly implicated module or sensor ?
Here are the possible errors from the scan tool, but I think the ones above predominate.
Quote:
Originally Posted by bluebee View Post
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
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Last edited by bluebee; 04-12-2015 at 11:59 AM.
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  #16  
Old 04-12-2015, 12:01 PM
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bluebee bluebee is offline
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Quote:
Originally Posted by bluebee View Post
(We need to summarize the half-dozen additional tests that can be done on a wheel speed sensor that can be done with the diagnostic tools).


What are the sum total of diagnostic tests that can be run on a wheel speed sensor, anyway?


Here's a very old summary, that doesn't include the live data from INPA which is suggested in earlier posts above...
Quote:
Originally Posted by bluebee View Post
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.)


Do we have a good summary of all the best methods of testing a wheel speed sensor?
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abs brake asc, abs brake dsc, bifecta, inpa, trifecta


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