Help with Longstanding ABS Issue

[stevick]

Hi gang, I have posted about this issue before, but it is unresolved and I am finally dead serious about solving this mystery. For the 5 years I have owned my '98 750iL I have had the triangle and ABS light on, a CEL for "no speed signal" and no cruise control (with a single "miracle" exception described in my prior post). I have always assumed the problem was with the RR wheel sensor, so I replaced it and swapped it with the LR with no change. I've cleaned the sensor and bore, and replaced the RR sensor connector, verified the X377 pin assignments, and confirmed the ~8 volt supply to it with a VOM. I finally acquired a handheld scanner that could read the ABS module, and the CEL fault code confirmed it was the RR wheel sensor, along with code for "42 supply voltage, wheel sensor". I cleared the CEL, which has not returned (yet), but the supply voltage fault returns immediately. So here's the where the strangeness comes in. Reading live data from the wheel sensors show ALL 4 sending data - up until it passes ~20km/hr., when the readout data goes blank and the scanner cannot reconnect to the ABS module - that is, until I return to low speed again or stop. In playing with the scanning, on a couple of occasions the DSC/ABS lights have gone out and cruise returned (working just as it should), but these occasions were short-lived. So I'm still trying to diagnose the issue. I believe the fact that data is being received from the RR wheel sensor (and the others) allows me to rule out a bad sensor, connector, and harness. That would seem to leave just the ABS/ASC+T module.

I watched Timm's video and read his write-ups on the subject, and they would seem to support the conclusion that it's indeed the module. Of course, I'm open to any other thoughts some of you may have. I went ahead and ordered a used ABS/ASC module with the same Bosch part no. (265 109 015) from a Lithuanian Ebay seller. I do understand I might need to have it coded, but I do have questions about that. First, could my swapping out the module cause any new (worse) issues? Second, is it possible that no coding would be required (e.g., if the module also came from a pre-facelift 750)? Third, what exactly is involved in the coding process - I assume I just swap the module and bring the car in. Lastly, is the coding, if required, doable by a noob who acquires the software, etc.? Also, can anyone tell me if there is any trick to unplugging the 83-pin connector on the ABS/ASC module (it's behind the glove box)?

Any help or suggestions will be appreciated.

[0239666]

I have the absolute exact same issue. Cleaned up and heat shrank new cabling on to the wheel sensors, lights went out for a couple of meters but back on which leads me to believe they were a problem but something else kicked in.
Installed and coded a new ABS control module (in the engine bay) didn't do anything. Probably didn't need to be changed. If you have a pre-charge unit (mine doesn't) you can test to see if it's working with a 12v supply. That has come up as a solution.
I've also read that broken cogs on the wheel that controls the cruise control can cause it to be erratic (which mine was but today it flat out turned off and pressing the cruise button won't bring it back on) but I haven't checked it yet.
Checked in where the level sensor is behind the CD changer (PITA to get to) because the metal bracket it's sitting on has been known to cut the wheel sensor cable. It was a little chaffed but definitely no cut. I put some foam in around it anyways. This probably isn't your issue as you are getting a reading for all the speed sensors on your thingy.
Checked for dampness in around the glove box and carpet but it's all good.

Are the thing under the glove box and the thing in the engine both called ABS module?

[stevick]

I'm disappointed to hear that a new ABS module did not work for you. I'll look into the pre-charge unit, but unlike later models, my car does not have the module attached under the hood that is subject to heat failure - only the module behind the glove box. I've never had, and do not have interior moisture problems. I thought about the "cogs" as a possible issue, but dismiss it (as well as some of the other more common problems, like the chafed wire) due to the wheel sensors sending data. Per Timm's excellent YT video, when the ABS/ASC+T modules fail (not uncommon), they can trigger trigger codes that are not accurate. The module I bought only cost $25, so it was a no-brainer purchase. No idea what the coding will cost and, as I noted in my OP, I am unfamiliar with the coding procedure. Much appreciate your thoughts and wish you luck with your issue.

[Timm]

Have you got one of these:



or an ASC+T module instead?

[stevick]

Timm, I have the ASC +T module.

[stevick]

Here's what I have under the hood
ABS Unit.jpg

Here's the module behind the glove box

ABS module.jpg

[stevick]

Went to turkey dinner at my sister's place and played with the scanner the whole way. Same issue - wheel speed data reports at slow speed up to ~20k/hr then reports blank data above that. Communicating with ABS module at the higher speed reports a communication error. Stop at a light and can recommunicate with module again and repeat. DSC/ABS lights on all the while. Get there, have dinner, and get in the car to return home. NO LIGHTS and cruise works the whole way home (10 miles or so). If history holds, the light will be back on when I next use the car. Somehow, the scanning is affecting the module function, at least temporarily.

[0239666]

Here's the module behind the glove box

ABS module.jpg[/QUOTE]

Do all E38's have this? It's the only thing left that I haven't tried.

[Mayorchuck]

You seemed to have covered everything. Do you know if the speed sensors are OEM?

[stevick]

Mayorchuck, I initially replaced the RR sensor with a Delphi - no change. I then swapped the rear sensors (LR was original to the car, moved to RR) - still no change. Given the diagnostic clues (i.e., sensor data is being sent to module, and intermittent full system function), I believe it safe to rule out the sensors. That seems to leave the module, presumably with some kind of internal fault.

0239666, I highly recommend a look at Timm's YT video: https://www.youtube.com/watch?v=tfP-8821Jwo Not every car has the interior module. My '99 750iL parts car does not - it has the large potted module bolted the valve assembly under the hood. My current driver, a '98 750iL (build date 06/1997) has what is pictured above. As Timm explains, the difference is the evolving technology BMW used for traction/stability control, so it seem model year dependent. I hope that helps.

I'm still hoping someone can give me some idea what is involved in coding the used module.

[GZilla]

Stevick, I had this issue with my E39 530i. This is a less common issue with E38s for whatever reason. I changed the sensors like you but to no avail. I then had my ABS module repaired by an ebay seller who does it as a service. From my understanding from what I was told by E39 owners in my private messages, putting in a used ABS module can cause issues because there was a cutoff year for the E39s when the ABS module changed. I wouldn't be surprised if that is the same for the E38. Likewise, it has to be coded specifically for your car. If you still have the old ABS module, I would suggest getting it repaired by one of those ebay services.

[Mayorchuck]

Mayorchuck, I initially replaced the RR sensor with a Delphi - no change. I then swapped the rear sensors (LR was original to the car, moved to RR) - still no change. Given the diagnostic clues (i.e., sensor data is being sent to module, and intermittent full system function), I believe it safe to rule out the sensors. That seems to leave the module, presumably with some kind of internal fault.

0239666, I highly recommend a look at Timm's YT video: https://www.youtube.com/watch?v=tfP-8821Jwo Not every car has the interior module. My '99 750iL parts car does not - it has the large potted module bolted the valve assembly under the hood. My current driver, a '98 750iL (build date 06/1997) has what is pictured above. As Timm explains, the difference is the evolving technology BMW used for traction/stability control, so it seem model year dependent. I hope that helps.

I'm still hoping someone can give me some idea what is involved in coding the used module.

I missed that it was not you that had replaced the module. I've never had to code one but I would think NSC Expert could do it easily if you have it.

[Timm]

A bit confusing this one, complicated by the fact that it is a 750! The module is for ASC+T and can be simply replaced as long as it comes from an M73 E38, no coding needed. It would be unusual for the module to fail, in fact, I've never heard of an ASC+T module failing - sure DSC modules fail every 5 minutes but not ASC+T.

Wheel sensors may be the problem - but so can the reluctance rings, do you know if half-shafts or hubs have been replaced?

- - - Updated - - -

[stevick]

Timm - I purchased the car with ~72k miles, now has 99k. No indications of half-shafts or hubs being replaced, but you never know. Given that I'm getting data readouts (at least at low speed) from all four sensors and anomalous short-lived full functioning, do you still believe I cannot rule out the sensors and the reluctors? I presume you have confirmed I have ASC+T from my photos in post #6, am I correct (I have no ASC button in the car, but I do have a DSC switch on the seat heater/defroster panel). Also, I have assumed this is not related, but a few years back, I replaced all the struts with coilovers, thereby leaving the EDC connectors to the struts unplugged and doing a delete of the SLS. That work did not give rise to the ABS issues, which predated the changeover.

The seller of the ASC module I ordered did not specify the model it came from, so I guess I'm rolling the dice on that. As you can see from this picture on the ebay listing,
asc on ebay.jpg
the Bosch number matches that of the installed module in my car (pictured in post #6). The BMW part no. for the module is 34521090921, which is shown as only used in 11/1993-08/1998 750s, so I felt it a fair risk. The only risk is if BMW used the Bosch part (0 265 109 015) to create other BMW parts for other models.

Mayorchuck - thanks for your input. I do not have anything other than a Peake and Creator C310 scantool. I assume my Indy can do it, if required, or worse case, the dealer.

Gzilla - Best I can tell, no one offers a rebuilding service for an ASC+T module.

[stevick]

Well it keeps getting stranger. I took the car out today for the first time since the Turkey Day run (where the DSC/ABS lights were all out for the return trip). I fully expected the lights to return, but they did not. Full functioning of the ABS and cruise was still there. I literally did nothing other than scan the ABS module, clear the fault codes, and read the wheel sensor data. In the past, the faults would reappear on the next trip, but not this time. I have not scanned again for fear it could reverse my good luck. I'm becoming increasingly convinced that the use of the scanner is affecting the module's function - in this case positively.

[tomloans]

Well it keeps getting stranger. I took the car out today for the first time since the Turkey Day run (where the DSC/ABS lights were all out for the return trip). I fully expected the lights to return, but they did not. Full functioning of the ABS and cruise was still there. I literally did nothing other than scan the ABS module, clear the fault codes, and read the wheel sensor data. In the past, the faults would reappear on the next trip, but not this time. I have not scanned again for fear it could reverse my good luck. I'm becoming increasingly convinced that the use of the scanner is affecting the module's function - in this case positively.

Make sure you don't have some sort of short or connection problem. I just read through this thread for kicks and it sure is looking like an intermittent connection issue due to either a short, corrosion or a bad ground. Be sure to clean the connector back at the RR wheel sensor cable and at the abs connection as well. Because if it is a bad connector, you can swap all the wheel sensors and it will still be problem.

Use...

https://www.amazon.com/CRC-05103-Ele...66032540&psc=1

Be sure to unbutton the battery before you do this. Be sure to let the light on the left side of the trunk turn off first before you unbutton the battery.

Also check and see if you have continuity - somebody can chime in if they know how. Follow the line and see if you notice a cut or separation. Is this an east coast vehicle, hence lots of rust.? All my vehicles are 20+ years old and weird grounding and corrosion issues will start showing their ugly heads. Anyways, just some thoughts as I have had experience with other vehicles with grounding problems, and such, but not with the e38 so I am educated guessing only. Best wishes.

[stevick]

tomloans - The car is a Florida car, essentially rust-free (no northern snow/ice/salted roads). I absolutely agree that some sort of intermittent connection is involved. While I have cleaned and tested the sensor connector, I have not unplugged the 83-pin connector on the module to check or clean the pin connections (which is interior to the car, not likely to have corroded, but not impossible). Likewise, I have not yet checked continuity on the sensor-to-module wiring (but I am aware of how I can do so, as I have the WDS pin assignments on the module connector). Your points are very well taken; and if the problem returns (which I still expect it will), I will clean the connections and try to check continuity. The used module is on its way on the slow boat from Lithuania, so if the connections aren't the issue, the replacement module will hopefully do the trick.

[0239666]

Well it keeps getting stranger. I took the car out today for the first time since the Turkey Day run (where the DSC/ABS lights were all out for the return trip). I fully expected the lights to return, but they did not. Full functioning of the ABS and cruise was still there. I literally did nothing other than scan the ABS module, clear the fault codes, and read the wheel sensor data. In the past, the faults would reappear on the next trip, but not this time. I have not scanned again for fear it could reverse my good luck. I'm becoming increasingly convinced that the use of the scanner is affecting the module's function - in this case positively.

I guess that leaves me all alone with my fault lights. What are the chances of I clear my codes it stays off too? Was the ABS and cruise not working before you cleared the codes?

[stevick]

Update: I have made a least a dozen trips of 5 miles or more since the Turkey Day "miracle" - still no lights and ABS/cruise is still working fine. I finally re-scanned and there are no fault codes in the ABS module, not even the persistent "42 supply voltage, wheel sensor" that had previously continued to return after clearing. The scanner still reads live wheel speed data, but still drops communication with the ABS module above 20kph (which returns when I reconnect at a lower speed or stopped). I received the used module I purchased, but have decided not to fix what ain't broke (for now). Even if the faults don't return, my curiosity might overcome my laziness and I might try the new module to see if it communicates differently. Overall though, I'm tentatively chocking this one up as a win.

0239666 - Obviously, I can sympathize, as I had lived with the problem for 5+ years. I wish I could tell you precisely what corrected the problem, but frankly I'm perplexed myself. Neither ABS or cruise was working before I obtained the C310 scanner, which for the first time allowed me to access the ABS module data. Initially, clearing the fault codes with the scanner resulted in the dash lights going out, but the lights and "42 supply voltage, wheel sensor" fault (and no ABS or cruise) immediately returning upon a driving. It was not until I used the scanner to access the real time speed sensor data that things seem to have changed, but not even the first time doing so - it took few tries. My crude understanding is that the scanner cannot affect the underlying problem, though clearing a transient fault code in the ABS module memory may allow the module to reverse the ABS system safety shutdown (which triggers the dash lights) occasioned by the fault. No idea why cruise is affected, unless the ABS shutdown also shuts off the RR data feed to the cruise module. As I think you can see, I'm shooting in the dark here. Hopefully, this was some help to you or better yet, may prompt someone more informed to chime in. Best of luck!

[0239666]

0239666 - Obviously, I can sympathize, as I had lived with the problem for 5+ years. I wish I could tell you precisely what corrected the problem, but frankly I'm perplexed myself. Neither ABS or cruise was working before I obtained the C310 scanner, which for the first time allowed me to access the ABS module data. Initially, clearing the fault codes with the scanner resulted in the dash lights going out, but the lights and "42 supply voltage, wheel sensor" fault (and no ABS or cruise) immediately returning upon a driving. It was not until I used the scanner to access the real time speed sensor data that things seem to have changed, but not even the first time doing so - it took few tries. My crude understanding is that the scanner cannot affect the underlying problem, though clearing a transient fault code in the ABS module memory may allow the module to reverse the ABS system safety shutdown (which triggers the dash lights) occasioned by the fault. No idea why cruise is affected, unless the ABS shutdown also shuts off the RR data feed to the cruise module. As I think you can see, I'm shooting in the dark here. Hopefully, this was some help to you or better yet, may prompt someone more informed to chime in. Best of luck!

https://www.amazon.com/Creator-Scann.../dp/B09SH1W676

Is this the device you used? I'm thinking of getting it as I'm all out of ideas.

[stevick]

No. The scanner you linked is the C301. The one I used is the Creator C310, which is also available on Amazon for ~$50, and is BMW-specific. It can read and clear codes from most modules and read some live data. Clears air bag faults.

BTW, my problem seems to have been wholly resolved, as no lights have returned and everything is still working as it should.

[0239666]

No. The scanner you linked is the C301. The one I used is the Creator C310, which is also available on Amazon for ~$50, and is BMW-specific. It can read and clear codes from most modules and read some live data. Clears air bag faults.

BTW, my problem seems to have been wholly resolved, as no lights have returned and everything is still working as it should.

Ordered. Get ready for a tsunami of error codes.....

[RHP]

The turkey is the only common theme running through the thread so I would refocus there. All kidding aside, I had Trifecta/ABS issues in both my e38s, a 1997 and with my 2001. I never did solve it in the 97 but replacing the pre-charge pump with a used eBay one solved it in my 01. I realize nothing I have said here is probably helpful. But I do feel your pain. My dad used to put electrical tape over any lights on the dash that he did not like looking at....

[Dushan]

Make sure you don't have some sort of short or connection problem. I just read through this thread for kicks and it sure is looking like an intermittent connection issue due to either a short, corrosion or a bad ground. Be sure to clean the connector back at the RR wheel sensor cable and at the abs connection as well. Because if it is a bad connector, you can swap all the wheel sensors and it will still be problem.

Use...

https://www.amazon.com/CRC-05103-Ele...66032540&psc=1

Be sure to unbutton the battery before you do this. Be sure to let the light on the left side of the trunk turn off first before you unbutton the battery.

Also check and see if you have continuity - somebody can chime in if they know how. Follow the line and see if you notice a cut or separation. Is this an east coast vehicle, hence lots of rust.? All my vehicles are 20+ years old and weird grounding and corrosion issues will start showing their ugly heads. Anyways, just some thoughts as I have had experience with other vehicles with grounding problems, and such, but not with the e38 so I am educated guessing only. Best wishes.

As I am in the process of chasing this same issue in my 2001 740iL (332k km) here are some of the observations I made. The 3 lights come on sporadically. Sometimes they are not on as I start the car and drive for a while, but if the road is wet they come on (not always). They have been known to come on when going into car wash (no roof leaks as I tape it before entering car wash).

Other times the light start as soon as the car starts but after 20 minute drive if I stop and shut it off for a few minutes they don't come back on.

I am starting to suspect a contact/cable. I have new sensors (all 4) and will have them installed in a few weeks. In the meantime I will check the cable near the CD charger (that's a new one for me).

I don't think that I ever tried cruise control with the lights on, but suspect that it would not be affected as the speedo is always working.

[Timm]

That sounds like your standard DSC module problem - intermittent!