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

Originally Posted by GSned

I have a friend who works for BMW who hooked up the car to the diagnostic machine which said it was a brake pressure sensor fault.

By now, you've seen Bill's consistent posts that the diagnostic machines can't tell you what you need to know because they're all hooked up wrong (I'm surprised we know that but the BMW technician does not know that - or - maybe the BMW tech knows something we don't know ...).

But anyway, I "suspect" you're wasting your time testing the brake pressure sensor (even though Carsoft told me it was that was what was stored in my car also, I learned to ignore it). To my knowledge, I don't think ANYONE here yet has actually needed to replace the pressure sensor. (If they have, they should come forward now - and provide proof with a before/after picture.)

Please post a picture of your flying-leads setup as you will be the FIRST person here to have done this so you should give back to the team and enlighten us.

Originally Posted by truelies

Hydraulic Pressure Sensor and the brake Pressure Sensor are same thing, is that correct?

That's how most of us seem to be using the terms.

Originally Posted by bluebee

By now, you've seen Bill's consistent posts that the diagnostic machines can't tell you what you need to know because they're all hooked up wrong (I'm surprised we know that but the BMW technician does not know that - or - maybe the BMW tech knows something we don't know ...).

With all due respect, this is a bit over the top. There is a lot more that the BMW "diagnostics machines" can do than just read fault codes, which seems to be the only thing you and Bill have done with "diagnostic machines." The fault code itself is not mean to be a diagnosis.

What makes you think the BMW diagnostic machines are "hooked up wrong?" They scan for fault codes and then provide a series of tests to determine what the cause of the fault is. It's no different in principle from what you and Bill recommend, except that the BMW diagnostic equipment allows you do more extensive testing than just measure resistances and voltages. For example, the software that the BMW diagnostic machines use (e.g., INPA, DIS) allows the tech to activate the ABS/DSC components (e.g., DSC pump and valves, precharge pump) and measure pressures, among other things. The pressure sensor test via the precharge pump is much more reliable than the pressure sensor voltage tests that you and Bill have suggested.

Originally Posted by jeffstri

There is a lot more that the BMW "diagnostics machines" can do than just read fault codes, which seems to be the only thing you and Bill have done with "diagnostic machines." The fault code itself is not mean to be a diagnosis.

You know that the fault code isn't a diagnostic solution; I know the fault code isn't a diagnostic solution; Bill knows this also ... but tell that to every Tom, Dick, and Harry that writes in that says "My mechanic says it's the brake pressure sensor".

How do I tell that person that what they are being told "is the problem" is merely the manifestation of the problem?

I do not know how to do that. It's easy to 'say' but it almost never sinks in.

Therefore, I don't know a "nice" way to get the point across. Do you? Bill has tried. Many times. Very many times. I generally tell them to read what Bill said.

You understand what Bill said (even without reading it, as I can tell from your words); but you're not the scores of people who think all they need to do is replace this part or that sensor because it showed up in the "diagnostic test".

The simplest thing to tell them is that their mechanic doesn't have a clue what he's doing. It's not correct ... but how else do you actually get the point across to the myriad of people (and they keep coming) who think the "magical diagnostic scanners" will flawlessly pinpoint the specific bad part so they can just go out and replace it themselves?

BTW, at least the last poster actually fabricated the flying leads to further test the brake pressure sensor ... but how many people do that? (I didn't even bother ... and I'm really really big on diagnostics.)

I don't profess to fully understand why, but, I have been here since March of 2008 and I don't recall a single person coming in who had a diagnostic done that truthfully pinpointed the problem when the (most common) problem REALLY was the one steel tack-welded wire on the Bosch 5.7 ABS control module lifting off it's gold bond pad or the extremely thin gold signal wires flopping against each other.

In that same time period, very many people have done diagnostic scans supposedly "pinpointing" various sensors, most commonly the brake pressure sensor and the steering wheel sensor in addition to the ubiquitous wheel speed sensors. Quite a few people have replaced 'em all (which is astounding to me), and in the end, they've had to have their ABS control module "rebuilt".

Bill has explained it far often than I can recall, in this thread, and in others (i.e., 540iman). Basically, the diagnostic tools are great at describing symptoms but not at pinpointing the actual problem.

The actual problem is most often either a bad wheel speed sensor (which is trivial to test with a DMM) or the ABS control module.

Blubee,

After I removed the ABS model, the 'bak' light is not on for my car. Is that normal? I saw you said after remove three will be on.

Originally Posted by bluebee

You know that the fault code isn't a diagnostic solution; I know the fault code isn't a diagnostic solution; Bill knows this also ... but tell that to every Tom, Dick, and Harry that writes in that says "My mechanic says it's the brake pressure sensor".

How do I tell that person that what they are being told "is the problem" is merely the manifestation of the problem?

I do not know how to do that. It's easy to 'say' but it almost never sinks in.

Therefore, I don't know a "nice" way to get the point across. Do you? Bill has tried. Many times. Very many times. I generally tell them to read what Bill said.

When Tom, Dick or Harry says "My mechanic says it's the brake pressure sensor," I’d refer him to a post (if there is one – or make a new one) that clearly explains the difference between fault codes and a diagnosis. Then I would ask him to go back to the mechanic and ask what the fault code(s) was and what additional tests he (the mechanic) did to isolate the problem. If his mechanic was an indy, he likely just scanned for fault codes. Even if he was a BMW tech (at a dealer), he may have only scanned for fault codes – it’s more cost-effective (and profitable) for a dealer to throw parts at a problem as we all know too well..

Originally Posted by bluebee

You understand what Bill said (even without reading it, as I can tell from your words); but you're not the scores of people who think all they need to do is replace this part or that sensor because it showed up in the "diagnostic test".

The simplest thing to tell them is that their mechanic doesn't have a clue what he's doing. It's not correct ... but how else do you actually get the point across to the myriad of people (and they keep coming) who think the "magical diagnostic scanners" will flawlessly pinpoint the specific bad part so they can just go out and replace it themselves?

I read all Bill’s posts in this thread before I made my first post, then re-read them before I made my last post, and just to be sure re-re-read them, and to simply say “read what Bill said” is very little help. If there’s a specific post of his which explains the difference between a fault code and making a diagnosis, why not refer Tom, Dick and Harry to it, or copy and paste the relevant part of Bill’s post, rather than make comments like “diagnostic machines can't tell you what you need to know because they're all hooked up wrong” or “their mechanic doesn't have a clue what he's doing”? I don’t think it’s the same Tom (or Dick or Harry) asking the same question here over and over again – Tom, Dick or Harry is almost always someone new, looking for information. Why not assume they can understand the difference between a fault code and making a diagnosis? You don’t have to re-create the explanation every time. If there’s already a good post, just refer to it or copy and paste.

Originally Posted by bluebee

I don't profess to fully understand why, but, I have been here since March of 2008 and I don't recall a single person coming in who had a diagnostic done that truthfully pinpointed the problem when the (most common) problem REALLY was the one steel tack-welded wire on the Bosch 5.7 ABS control module lifting off it's gold bond pad or the extremely thin gold signal wires flopping against each other.

In that same time period, very many people have done diagnostic scans supposedly "pinpointing" various sensors, most commonly the brake pressure sensor and the steering wheel sensor in addition to the ubiquitous wheel speed sensors. Quite a few people have replaced 'em all (which is astounding to me), and in the end, they've had to have their ABS control module "rebuilt".

Bill has explained it far often than I can recall, in this thread, and in others (i.e., 540iman).

Probably because they just had fault codes scanned, just like you had initially, not a diagnosis.

Originally Posted by bluebee

Basically, the diagnostic tools are great at describing symptoms but not at pinpointing the actual problem.

This is simply not correct. You (and Bill) continue to confuse (or maybe just obscure) the differences between fault code scanners (e.g., Carsoft 6.5) and “diagnostic tools” and between a fault code and a “diagnosis.” (By obscuring, I mean you often will say “diagnosis” when it appears you mean fault code.)

Bill apparently has only used Carsoft to read fault codes, except for one case where he did some work with a buddy who had INPA and Progman, but it’s not clear exactly what he did.

I don’t know how to make any clearer to you that BMW diagnostic tools such as DIS and INPA (and probably newer versions of Carsoft) do a lot more than read fault codes. The first thing you do with DIS is read fault codes. DIS then leads you through a series of additional tests to try to pinpoint the problem (i.e., make the diagnosis.) Some of the tests involve checking wires and connectors for continuity and shorts to ground, and resistance and voltage measurements, as you and Bill came up with for wheel speed sensors. Others are measurement of pressures and activation of components, which you do within DIS – no additional equipment is needed. Does DIS always pinpoint the problem? No – sometimes you do end up throwing parts at a problem, but less often than otherwise.

Originally Posted by bluebee

The actual problem is most often either a bad wheel speed sensor (which is trivial to test with a DMM) or the ABS control module.

True, but pressure sensors, precharge pumps and other components do fail too.

Originally Posted by jeffstri

I'd refer him to a post (if there is one – or make a new one) that clearly explains the difference between fault codes and a diagnosis.

Very interesting. Very well written post. Good healthy discussion.

You sir, will change opinions. Let's see what we can do together.

Where should we refer them for diagnostic hints when they have the ABS BRAKE DSC trifecta, yet, they say "my mechanic read the codes and says it's" (a) the hydro unit, or (b) one of the three steering angle sensors?

Note: If the mechanic says it's the (c) wheel speed sensor, we can provide six diagnostic tests.
If the mechanic says it's the (d) brake pressure sensor, again, we already provide diagnostic tests.

And, why don't we ever hear anyone tell us that the fault codes directly indicate (e) the ABS control module itself?

Originally Posted by jeffstri

I read all Bill's posts in this thread before I made my first post, then re-read them before I made my last post

You know, I don't believe most of what I read here (of what people did); but I "do" believe you. You are spot on.

Let's be blunt.

I don't really know what to tell them when they are told by their mechanic that the ABS BRAKE DSC trifecta is due to a fault code implicating something other than the ABS control module.

Most often the mechanic tells them the fault codes indicated the:

• wheel speed sensor
• brake pressure sensor
• steering angle sensors
• hydro unit

Rarely, if ever, do I see someone coming here who says the mechanic's fault codes indicated the ABS control module itself.

So, if it's the wheel speed sensor, I tell them to run one or more of the six tests.

If it's the brake pressure sensor, I tell them to run the flying-leads test for voltage as you press on the brake pedal.

For steering angle sensors, I point them to the MAX_VQ BMW PDF explaining the DSC system.

And I have no idea what to tell them when the fault code indicates the hydro unit.

It's important to note that most of the time, it's none of these things (time and time and time again we find that out anecdotally). With the trifecta, it's most often the wheel speed sensors or it's the ABS control module ... which nobody (even I fell into this trap) wants to believe, at first.

Originally Posted by jeffstri

If there's a specific post of his which explains the difference between a fault code and making a diagnosis, why not refer Tom, Dick and Harry to it

Maybe we need a separate thread specifically on the difference between a "fault code" and "making a diagnosis" specifically for the ABS BRAKE DSC trifecta!

The intent would be to refer people to THAT post when they tell us "my mechanic said it was the < fill in the blank >".

Originally Posted by jeffstri

Why not assume they can understand the difference between a fault code and making a diagnosis?

I am not sure I fully understand that, in practice myself, when it comes to the ABS trifecta.

Sure, I know that the fault code is what the computer senses isn't giving the right values - and I certainly realize it could be something else altogether - which is why you need the diagnosis ... but in the specific case of the BRAKE ABS DSC trifecta, I'm not sure what you're suggesting as the diagnosis (given the various fault codes that we know pop up) implicating the wheel speed sensors, the brake pressure sensor, the steering wheel sensors, etc. ... but almost never (if ever) the ABS control unit itself.

How do we diagnose a bad ABS control module anyway?

Originally Posted by jeffstri

You don't have to re-create the explanation every time. If there's already a good post, just refer to it or copy and paste.

Bingo. I HATE re-creating the explanation every time! It's just plain silly for a whole bunch of reasons. You think like I do.

We make the explanation ONCE ... and then we refer people to THAT well-done explanation. Everyone wins. And the next person stands on our shoulders.

However ...

Given what you've said, I do not know if we actually have a good explanation.

Here is what I have been referring people to (from post #36 of the best links):

see Bill's 'logic' of testing ABS sensors).

Do we have something better?

Originally Posted by jeffstri

Probably because they just had fault codes scanned, just like you had initially, not a diagnosis.

Here, for example, is what I've been referring people for fault codes (from post #48 of this thread):
- carsoft.pdf (127.3 KB, 2912 views)
- peake-codes-e39.pdf (410.1 KB, 1305 views)

I realize the difference between dumb reading of a fault code and a proper diagnosis ... but ... I do not know what to tell people for a proper diagnosis when they have the ABS BRAKE DSC" trifecta.

Up until now, the only thing I can tell them is what people told me:
- If you have the ABS BRAKE DSC trifecta ...
- Test the wheel speed sensors (repair or replace any bad ones)
- If all are good, then repair or replace the ABS control module

The assumption is that the fault code (almost all of them in this particular situation) is "really" telling you there's something wrong with the ABS control module. (And which is very often fixed by repairing the ABS control module ... so ... they were right.)

But ... how do you PROVE it was the ABS control module.
I'd love to know how!

Remember, I spent a year trying to do that (and failed!).

It "was" my ABS control module ... but I couldn't "prove" it with a diagnostic test!

What you're saying, I think, is we're missing a whole slew of "diagnostic" tests, especially when the fault codes indicate various other sensors (most commonly the brake pressure sensor and the various steering wheel sensors) and not the ABS control module, per se.

I won't disagree. We are missing those diagnostic trees.

With the little that I know, if someone asks for diagnostic tests for the 20 or so inputs to the ABS, I'd refer them to this BMW PDF from Max_VQ in post #61 of this thread:
- DSC part 1.pdf (988.0 KB, 1572 views)
- DSC part 2.pdf (771.1 KB, 1711 views)

From that PDF, they can build their own diagnostic setup (just like I tried to build flying leads for my brake pressure sensor fault code).

And, I refer them to this PDF from post #48 of this thread:
- carsoft_explained.pdf (643.2 KB, 2418 views)

Which "purports" to provide diagnostic hints (but I wonder what you think of that).

Originally Posted by jeffstri

I don't know how to make any clearer to you that BMW diagnostic tools such as DIS and INPA (and probably newer versions of Carsoft) do a lot more than read fault codes.

I have NEVER used any of those tools (other than the older Carsoft); and, I've tried to get information about them here but failed for the most part.
- Description of Carsoft, GT1, INPA, DIS, EDIABAS, & Peake (1) & which can modify the auto-lock car door feature (1) & what does Carsoft do anyway (1) (2) (3) (4)

In summary, we need to point people to diagnostic tests for the key fault codes that come up during a BRAKE DSC ABS trifecta.

Given that most of the time it's the ABS control module, and almost all (all?) the time the fault codes do not implicate the ABS control module per se ... the question becomes ...

Q: Where should we point people with the trifecta who have been told by others the fault codes report a bad sensor and not a bad ABS control module?

Given the most common fault codes implicate the following:

• wheel speed sensor
• brake pressure sensor
• steering angle sensors
• hydro unit

And, the most important diagnostic question of all:

Q: How do we diagnose a bad ABS control module?

Today, yet another older-E39 owner asked for the pinout to test their ABS control module and four wheel speed sensors!
- ABS light came on and now speedo is doing weird stuff.

What we need (exasperatingly), is someone like Bill or me or QSilver or Cn90 (etc) who has the OLDER model E39 to simply post the test points on the connector (see below) to test!

Reproduced below, for convenience, are (what I think are) the relevant pictures for that older-model E39.

I ask for a volunteer to annotate the proper photo below with the pinout for the four wheel speed sensors!

Bluebee,
You asked me to post pics of my set up for back probing the pressure sensor, unfortunately I opted for a very crude method of piercing the insulation on the 2 lives and checked the voltage that way.

I completely agree with you regarding mechanics (technicians) hooking up diagnostic machines, pulling codes and diagnosing the problems that way. The guy I use is a BMW technician with his own BMW dignostic equipment.
Im not a mechanic or tech, I opt for problem solving using research and a common sense approach which in my case told me it wasnt the pressure sensor due to fact I had various different symptoms at different times, I guessed if it was sensor then it would be same symptoms all the time.
I put this theory to my mechanic who replied saying" sometimes you have to trust the machine" Easy when its not his cash I guess!

Anyway I stuck with my theory and got my hands on a second hand module, fitted it and problem instantly sorted.
I took the old module apart for a look. I dont know how you would ever repair those tiny hair like wires, I touched them and they all fell off, I think you would have to be a micro surgeon to resolder them.

Ive read a few folk going on about getting second hand modules coded. My car works perfectly with this new module with all functions restored. Is there any reason why I should have the module coded?
I was going to ask my tech!!

Cheers

Originally Posted by GSned

method of piercing the insulation on the 2 lives and checked the voltage that way.

Thanks for the update (I was wondering). BTW, nobody yet, as far as I can tell, has "ever" reported that replacing the brake pressure sensor has solved the trifecta, despite many people (including me) reporting the code for it.

Originally Posted by GSned

got my hands on a second hand module, fitted it and problem instantly sorted.

Good for you. In general, either the larger steel wire lifts off its gold bondpad (you check with a magnetized needle) or the angle-hair-thin gold wires flop about due to some sort of defect with the snot-like goop that's supposed to prevent that from happening.

Originally Posted by GSned

I took the old module apart for a look.

We'd LOVE to see a picture of it!

Originally Posted by GSned

I dont know how you would ever repair those tiny hair like wires

I think the only "repair" so far has been to separate them from touching and applying new goop to prevent them from flopping about.

See:
- ABS control module autopsy (specific instructions necessary for a competent repair

Originally Posted by GSned

Is there any reason why I should have the module coded?

Funny you should ask.

I think it's clear by some accounts that you "must" code the VIN; yet, by other accounts, it's not so clear what actually happens if you don't bother.

Here is the thread for you to add your experience to:
- What happens if you don't code the VIN into a new ABS module?

BTW, QSilver7 just posted a very nice set of charts for debugging left rear wheel speed sensor implications over here.
- Troubles in River City, ABS? Battery?

I'll save the documents here (for one-stop shopping) but interested parties need to read his post as there is more there than just the attachments.

Regarding recoding my new ABS module, I contacted my tech last night who told me that the car runs a self diagnostic every 200 miles or so and if I were to leave the module as is then the car would detect something is wrong and all 3 lights would come back on!!!!!

So for the sake of £50 or so ive arranged for him to code it today.

Better safe than sorry I say.

I will try post a pic of the old module although you mentioned the heavy guage wire in the middle, mine didnt have that and all wires were silver mine is the DSC111 Bosch 5.7, either way I think you would have to be a magician to fix it.

Cheers guys

Originally Posted by GSned

the car runs a self diagnostic every 200 miles or so and if I were to leave the module as is then the car would detect something is wrong and all 3 lights would come back on!!!!!

I'm confused. Would the three amber lights (BRAKE/DSC/ASC) go back on or would something "else" happen as intimated in this thread:
- E39 ABS Module, what if one does not code the VIN

So far, we have highly inconsistent data points, but, what happens after 200 miles may also depend on the delta between:

• The transmission coding (A or M) of the old module versus the new
• The engine model & year coding of the old module versus the new

Originally Posted by GSned

I will try post a pic of the old module although you mentioned the heavy guage wire in the middle, mine didnt have that and all wires were silver mine is the DSC111 Bosch 5.7

Please do post a picture!

Nobody is going to help us (or the next guy) except us together, as a team!

For that, every single bit of information is precious. Bill ripped open his friend's ABS control module, for example, as a sacrificial lamb ... and I had to (travel the Internet) go to Russia to find out about the steel wires!

See:
- removing "snot-like" goo from ABS circuit board- Bluebee pls. read!

Bluebee ive attached a couple of pics from my old module and as you can see i made an attempt at fixing it by trying to resolder the fine wires back on, without success as you can see.

Well I got my new module coded to the car today. Its all very vague and confusing, I was quizzing my tech today as to the consequences of not coding the new one to the car. He says that the numerous computers in the car talk to each other and the car would work out that the module was not the right one for the car as these modules store a lot of info for example when he plugged my car in today with the new module already fitted the info he was reading was that of the donor car, he could tell me the vin and millage from the donor car as this was the info displayed therefore he had to code it so as not to confuse cars computers as some would register my cars millage and the ABS module was still showing donor cars millage, which would confuse car causing problems.

OR SO HE SAID!! I still have my doubts as he said the VIN number cant be changed, once a VIN is registered in the memory this can never be changed or removed and he couldnt get the millage exactly to match my car so therefore in my humble opinion the whole operation was pointless but according to him it had to be done.

Ive probably given you more questions than asnwers but thats what Ive been told so im passing it on.

Cheers

Originally Posted by GSned

Ive probably given you more questions than asnwers but thats what Ive been told so im passing it on.

Yes!

I don't disagree with anything you said. Since I had my own module rebuilt, I didn't have to deal with the VIN recode; so I was asking for others.

I guess, what we need, is for someone to "rent" an E39, switch modules, drive for more than 200 miles, and THEN we'll find out what really happens!



Sorry about the unsuccessful repair. Here is the workup of one of the successful repairs.
Thanks for the pics. We should put them into Bill's ABS control module autopsy thread for future reference!

For the record, even though I don't have an older E39, RustyZipper and I are trying to help those with the older E39, by pro-actively annotating the connector with the pinout to test the four wheel speed sensors.



We need to know a few questions ... here is where we are at the moment:
- Troubles in River City, ABS? Battery?, by Rustyzipper

In summary, I could annotate the procedure for the older E39s if I only knew:

1. Which connector?
2. Where is that connector?
3. Where is pin #1 and where is pin #88 on that connector?
4. Then, I could label pins #10, #11, #12, #13, #14, #15, #18, & #35.

Given that the older BMW E39 wheel speed sensors are at:

• Left front wheel speed sensor (pins #35 & #10)
• Right front wheel speed sensor (pins #14 & #15)
• Left rear wheel speed sensor (pins #12 & #13)
• Right rear wheel speed sensor (pins #18 & #11)

Originally Posted by bluebee

1. Which connector?
2. Where is that connector?
3. Where is pin #1 and where is pin #88 on that connector?
4. Then, I could label pins #10, #11, #12, #13, #14, #15, #18, & #35.

The WDS reveals all

Thanks for that pinout and location for the connector to test on the older E39s.

If I didn't make a mistake, here is the relevant diagram for anyone wishing to test the diode drop and resistance of their four wheel speed sensors on the older E39.

Notice that there do NOT seem to be metal contacts in the holes apparently designated below for the wheel speed sensors ... so we'll need someone with the older E39 to doublecheck our diagram below.

Also note that I have no idea which is the forward-biased direction and which is the reverse (I figured it out on my newer model E39 by trial and error); so, again, I ask the next older-E39 that undergoes a wheel speed sensor diode drop and resistance check to let me know which directions are what.

Originally Posted by bluebee

Notice that there do NOT seem to be metal contacts in the holes apparently designated below for the wheel speed sensors ... so we'll need someone with the older E39 to doublecheck our diagram below.

It is hard to tell from the picture but it looks to me like the holes (10-15, 35, 38) for the wheel sensor contacts are populated. Compare them with 8, 16, 17, and 20 in the top row and 41, 45, and 47 in the middle row which are not used.

Originally Posted by bluebee

Also note that I have no idea which is the forward-biased direction and which is the reverse.

Again, the WDS reveals all. In all the wheel speed sensors, new and old, pin 1 is the speed sensor output and pin 2 is the voltage supply for the sensor:

Originally Posted by jeffstri

the holes (10-15, 35, 38) for the wheel sensor contacts are populated.

Working TOGETHER - we'll solve this problem!

Thanks for that extra information. Working together, we can finally solve the pinout question for others.

Today, in this thread, a user (yet again) couldn't get any readings:
- ABS light came on and now speedo is doing weird stuff.

This isn't the first time a user couldn't get any readings (nor will it be the last), so, as a prophylaxis, I took the liberty of attempting to add the power and ground points to the pinout connector.

Is it reasonable to ask the users to doublecheck their voltage readings using the power and ground connectors (and continuity to ground) so as to ensure they're actually making contact with their probes?

Here is your excellent addition, with those of others, put together!

Below are the results from my tests a year ago on my newer-model E39.

Note that the forward biased readings are different from the reverse-biased readings, which, if someone is having problems, should be looked for to see if they're using the correct technique (most of them aren't).



So, to stave off confusing for the people who use the diagram we created today, I just now added (in red) a note about the biasing directions.

*******> ********>

Originally Posted by Max_VQ
*******>********>

I just now reassembled the 30-page Max_VQ DSC PDF, which is a must read for anyone with any DSC or ABS or sensor-related problem!

- All about DSC and the score of ABS DIY related sensors from MaxVQ including steering angle and wheel speed sensors (1)

Hi Bluebee/All ABS Traction experts,

I have been following your thread and work for over a year and many thank for such a wealth of information.

Following my own ABS/traction indicators lighting up on my dashboard and no speedo I followed your thread and played with speed sensors and trying to get a multimeter to work. Eventually I sent off thye module to BBA in the UK as I'm UK based. Following the rebulid everything was good for a few weeks and then it failed again, but initially only once every through weeks. However it got worse through the winter and I now coming up for my MOT (UK vehicle check) which if you have and ABS light on is an automatic fail in the UK.

Given the issues were exactly the same as as previous althougth the speedo now continue to work when the ABS/ASC traction lights trip and my autobox has not flipped into failsafe which happened previously I sent the unit back to BBA under warranty. They say they cannot find fault with it and are returning it to me.

So today I set about testing the pins from the ABS connector. I should point here that my car is a 2001 e39 525SE Touring with ASC which I believe differs from the the US spec cars of that year which I belive are all DSC. In the UK DSC was an optional extra on an SE and only standard on a Sport model I believe. Anywas the point is the ABS module is essentially the same with the same pin locations. The car does have 4 speed sensors, one on each wheel.

Anyway I put a new 9V battery in my DMM and set about the test. Interesting as other have posted the diode test yielded no results at all. Given this has been reported by several others maybe this relates to the tpye and specification of the DMM used my is a cheap one £10. However, setting the unit to 20M ohms I achieved the following readings in one direction only:

Left rear, pins 13 &29: 13.47

Right rear, pins 30 & 31: 13.39

Left front, pins 28 & 12: 16.20

Right Front, pins 15 '& 16: 14.31

While the values differ from others posted Looking at consistency it appears that the Left front is rather higher than the others.

Last year I started removing and cleaning my rear speed sensors and I though on of these was the culprit as the speedo had failed. They were filthy and I cleand both them and the rings with cotton buds but did not touch the fronts.

Now with these readings do you think it is possible that muck alone could affect my reading, or more likly a replacement sensor is needed. My initial thoughts are to remove and clean the front sensors and rings and then see what the reading are before I buy a new sensor.

Interesting I also have a spare rear sensor which reads 12 on the 20M setting, or 1.849 on the 2M ohm seeting on the DMM again in one direction only.

Any thoughts/cpmments much appreciated!

Apologies for all the typos.

Done in a rush while being distracted............

I recently had the DSC light come on (the one with the exclamation point & triangle and circular arrow.) I've had it on for around 450 miles, and none of the other lights come on. I don't know if it matters, but I saw the DSC light come on as I was making a right turn.

Anyway, I gave it a few tries to test it according to Bluebee's DMM procedure (which is a great write up, thanks!) I'm guessing I'm too dumb to figure out the DMM. I have the DMM set on the diode icon (I think that's what it is...see photos below...)

I have attached AWG22 wire to the leads, and inserted them into the larger square holes (the ones without the beveled housing) but nothign seems to happen. My cheapo Harbor Freight DMM reads 1 when the leads are not touching. But when I touch the leads together, I get some jumbled, random number, which I interpret to mean that the leads are working/making contact.

When I insert the leads into the connector, I still get the reading of 1, which seems to mean nothing is happening. I've tried the connectors for all 4 of the DSC sensors, and still the same 1 reading.

What am I doing wrong here?

The leads are in the 13 and 29 holes.



When I touch the leads together, at least I get some reading.