Intermittent ABS Brake DSC light trifecta when turning steering wheel

[Manny G.]

Hello E38 forum, this is a new area of the forum for me.

I'm usually in the E39 or E21 section, but I recently picked up '01 740i M-sport with 180k miles all from the same owner and have been going through the car addressing the many neglected things the PO let go. The car had a good service history, and a TCG job done with receipt a few thousand miles ago and was at a steal of a price ... plus it was white so I couldn't resist.


Anyway, when I purchased the car, it had the trifecta of lights on, but the seller stated that they just replaced the ABS module and that it needed to be coded. He was partially right, because when I scanned the car with PA Soft at purchase, the SAS sensor needed to be calibrated also. I noticed the speedo needle wasn't moving when i took it on a test drive, I immediately thought of the rear driver/left side ABS sensor. The transmission was having a rough shift too but I didn't concern myself too much with this since I'd eventually be doing a manual swap. I bought the car and got it home, drove fine in S mode and in M mode. Oh, and the power steering system was completely shot,.. pump sounded like it had marbles in it.

I let the car sit a few days while I looked for parts of the small fix-it stuff that was bugging me like the armrest and lower windshield cowl plastic (more on why i jumped on this so quickly later), and then gave the car another full scan with PA Soft again. I'm using 1.4.0.9, and I have a jumper between the pins on the diagnostic cap so that I can connect through the cabins OBD port.

The scan came up showing these errors in the ABS and LEW:
ABS
21/FF - Wheel speed sensor front left, open circuit
61/FF - Steering angle adjustment necessary
20/FF - Wheel speed sensor front right, open circuit

LEW
09/CD - No CAN message (ASC)

I tried to clear the errors on both, but they would not clear.

Then I hooked up tool32, did the Steering angle adjustment job and got rid of the Steering angle adjustment message.

I turned the wheel lock to lock a few times to finish bleeding the power steering system I had just replaced after all this and also to see if it would trigger a new error with the sensor, but instead when I scanned the with PA Soft again, the ABS module came up with NO errors... both speed sensors errors cleared up and the LEW error for no CAN was now a shadow and not present. I was suddenly able to clear the error on the LEW.

I took the car out for a test drive to see if the trifecta stayed off, it did. I came back to the car about an hour later, trifecta on again.

I hooked up PA soft, turned on the car, scanned it and got:
ABS
51/FD - Pressure Sensor, open circuit
20/FF - Wheel speed sensor front right, open circuit

Tried to clear them, couldn't. Remembering what I did last time, I turned the wheel lock to lock, scanned it, different errors showed up, this time front left speed sensor, and still pressure sensor. I tried to clear it, the left speed sensor error cleared, pressure sensor stayed. Power cycled the car, scanned, same errors, couldn't cleat them.... turned the wheel lock to lock a few times, tried to clear the codes, THEY ALL CLEARED. The trifecta shut off and the LEW error was able to be cleared also. This is only temporary as the errors come back after driving around a little bit or letting the car sit.

Oh and the reason I replaced the windshield lower plastic trim so soon is because it was completely dry rotted and disintegrated and letting water pour all over the e-box .. When I opened the e-box, the 10pin engine connector had moisture residue on it and so did a transmission connector


Before I start replacing wheel sensors and pressure sensors and ABS modules again, is there something I'm missing? Would a failing SAS do this? Should I start checking wire harnesses around the ABS module?

[Timm]

All those errors point to the 'new' DSC module being faulty, especially as the errors are intermittent...

[Manny G.]

All those errors point to the 'new' DSC module being faulty, especially as the errors are intermittent...

I've figured out that I can clear the errors if I just turn the steering wheel back and forth enough times not necessarily lock to lock... I've done it at least 3 times now.

I was hoping the module wasnt bad, i'll have to find another one and try it out.. I'd try the one out of my 540 that is known good but i'd have to recode it, no?

[SilverV12]

I've figured out that I can clear the errors if I just turn the steering wheel back and forth enough times not necessarily lock to lock... I've done it at least 3 times now.

I was hoping the module wasnt bad, i'll have to find another one and try it out.. I'd try the one out of my 540 that is known good but i'd have to recode it, no?

I would always start with replacing any faulty wheel sensor, without it the system will never work properly.
That is what I did about 2 years ago but I knew my DSC module was bad so I bought a so called refurbished module from the same build year and month as mine so I didn't have to code it to my car but it never worked. Turned out I was "scammed", the module was never rebuilt. Only had new sealing stickers on the outside, I took my loss (nothing I could about it) and had my original module rebuilt.
After that all was fine and still is, I would recommend to have your original module redone.

Oh...I almost forgot; whatever you do, never buy the cheap aftermarket wheel speed sensors because they simply don't work or for a very short period of time. Waste of money...ask me how I know.
Always go for the original.

[kouks]

^ What he said, replace the wheel speed sensor, it may be the wiring on the speed sensor is broken and causing the issues as you turn the wheels. You may just want to remove yours and check for wiring cracks, did that with one of mine years ago, soldered back together, no problems. Or go get a good looking one from a JY to try out, unless you want to spend the cash.

[Manny G.]

^ What he said, replace the wheel speed sensor, it may be the wiring on the speed sensor is broken and causing the issues as you turn the wheels. You may just want to remove yours and check for wiring cracks, did that with one of mine years ago, soldered back together, no problems. Or go get a good looking one from a JY to try out, unless you want to spend the cash.

This.

I actually did this very thing yesterday afternoon... drove the car up on ramps and looked specifically at the connector boxes in the wheel housings for the ABS sensors. I only had to get as far as the front driver/left side to notice something was off... underneath all of the sludge from the old leaky power steering system was a frail broken blue plastic connector that was probably .2 seconds from just completely disintegrating. Also noticed the wiring for the brake pad sensor had the insulation cut and wiring exposed.. along with the Servotronic connector seemed to be ready to come apart too.

Luckily I ordered new sensors (VDO brand) and should be here by Friday.


Question for anyone who has put new connector heads on the harness for the ABS sensor... is it the same plug as the Servotronic and brake pad sensor? They *almost* all look alike besides the obvious color differences.

When I searched realoem for an ABS connector, its no where to be found in the catalog, but if I searched for the Servotronic connector, it shows as pn# 61131392246 , which when I search for to buy online takes me to ECS showing that its actually an ABS connector? https://www.ecstuning.com/b-genuine-...h/61131392246/

[stevick]

Just fought the same battle on the ABS wheel sensor connector (harness side). This was the right connector: https://www.fcpeuro.com/products/bmw...ol-61131392246. If you screw up pulling the pins from the old connector (like I did), here is the pin that goes in the connector: https://www.fcpeuro.com/products/bmw...et-61130005199. These did the job. Good luck with it.

[Manny G.]

Just coming back for an update on this, I cleaned up the wiring which wasnt as bad as I thought. The Servotronic connector is what was in bad shape. I still replaced both front speed sensors, but had same trifecta problem... then ordered a replacement ABS module, problem solved. I had to calibrate the steering angle sensor to get rid of the traction control light. The module I purchased was from a 2001 7 series, so i did not have to recode it.

[goinstrong]

Thanks for your last post. That is a nice looking E21 also!!

[Manny G.]

Thanks for your last post. That is a nice looking E21 also!!

Thank you!




So my ABS issue has taken a different turn now. I though that everything was fixed, but seems that now if i drive the car above 20-ish/25 mph, i get something that feels like a transmissions fault (no transmission faults found), and then the trifecta of lights lights up. The error on the new ABS module now is "Pressure Sensor, plausibility precharge pump". I can clear the fault from the ABS module, but then it will come back once i start driving above about 25mph.

Could a steering angle sensor/LEW have anything to do with this?

[Manny G.]

Just found this, matches my issue exactly,.. it suggests testing the precharge pump with 12V and seeing how it reacts.. its either dead or working.

http://www.meeknet.co.uk/e38/ABS/Index.htm

[ConvGeorge]

Matt at cheap-abs.com has treated me right on two different vehicles that needed abs module repairs. My 740 had problems with the speed sensor wires inside the module, and a bad MOSFET in the return pump driver.

[Manny G.]

I hooked up a 12v external power supply to the precharge pump and I heard nothing at all. Not a single noise. I then connected through INPA to test out the precharge pump, also heard nothing. I did test other functions and I can hear a pump working up near the ABS module... also an occasional clicking or zapping noise. but nothing seems to trigger anything out the pump near the brake fluid reservoir

[Manny G.]

Finally resolved the precharge pump issue. Picked one up out of a 2002 540 at the LKQ yard near me, took about 20 minutes to swap out... no more trifecta after 25 mph