[automan25]

Vehicle:
2010 E92 / N51 / 2wd / 328i / M-Sport

Issue:
A couple of days ago I had this warning pop up on my iDrive screen:
Driving stability! Drive moderately. Brake and drive control systems malfunction! Reduced braking and driving stability. Avoid hard braking.

There were some other warning lights as well; all pointing to something with the ABS and stability control systems. The car runs and drives fine but the cruise control, hill holder, and other ABS related features don't work. I also noticed that sometimes when braking and turning at the same time at low speed the ABS will feel like it's engaging causing a chatter in the brakes.

I plugged in my Foxwell 510 scanner, cleared the codes, and the only one that came back is:
2DEB/not present, DME: Power management, vehicle electrical system

Diagnosis (so far):
Someone online suggested that I check fuse 20 and 65. Both checked out fine.

Some research online suggests that the issue may be with the alternator. I measured the voltage at the battery charging terminals under the hood with a (Fluke) multimeter and got 12.4v with the engine off and 13.94v with the engine running and all accessories on. This seemed to be within the normal range. I then discovered that you can get to a 'hidden' menu in the dash to show voltage while driving so I tried that and got 12.1v with the engine off and never more then 13.2v while driving around with the accessories on. Those numbers seem low to me and not sufficient to charge the battery and run all of the accessories.

I decided to have the battery tested this morning just as a first step (since that's easy to do) and it tested out just fine. Before I remove the alternator and take it in for testing I thought I'd check here first and see if I'm going down the right path here.

Any thoughts would be helpful.

[gbalthrop]

Originally Posted by automan25

... 2010 E92 / N51 / 328i ... warning lights as well; all pointing to something with the ABS and stability control systems... 2DEB/not present, DME: Power management, vehicle electrical system... I then discovered that you can get to a 'hidden' menu in the dash to show voltage while driving so I tried that and got 12.1v with the engine off and never more then 13.2v while driving around with the accessories on...

BMW Fault Code Lookup, Fault Info Sheet for "2DEB" suggests that you had (NOT currently present) "Over-Voltage", or system Voltage > 16V with engine running & Alternator Charging.
https://bmwfault.codes/XMLDiagView?d...UANQA1ADAANAA=

You indicate that your "Hidden Menu 9.00" shows no more than 13.2V with engine running since the code was read. If you have NOT cleared the "2DEB" fault code in the DME, check to see what "Freeze Frame Data" (snapshot of system conditions when fault code saved) shows for KL87 or System Voltage.

Over-voltage, or Voltage > 16V can cause many different issues with bus communications. Multiple warning lights on the Instrument cluster, particularly DSC or ABS warning lights, are OFTEN caused by Over-voltage.

Your N51 Engine probably has the Bosch 180-Amp Alternator. Check the Part# and Mfr. Label on your Alternator. If so, then I would suggest investing $33 in a new Voltage Regulator:
https://www.autohausaz.com/pn/BS-12317561939

MUCH cheaper than a new Alternator at ~ 10x the price. Voltage Regulator is installed in rear of Bosch Alternator, and should be a DIY replacement.
George

[automan25]

Thanks so much. I appreciate your insight. That sounds like the cause. I do indeed have the 180-Amp alternator. I'll order the new voltage regulator and see if that takes care of the issue.

[automan25]

I replaced the voltage regulator; the old one was very clearly worn. This cleared up the 2DEB code but did not fix the ABS / stability control issue. I ended up also replacing the abs sensors at each of the front wheels and that took care of the initial issue. Thanks for the help gbalthrop.