E39 ABS/DSC help needed

[Ross]

Both ASC and DSC lights have popped on in the womans E39 ('99 528ia). Both systems are verified inoperative.
The first occurance was with me behind the wheel accelerating full throttle through a turn. After a few on/off cycles the lights extiguished by themselves and normal operation was restored.
They came on and then later off again one time subsequent to that before finally now remaining on always.
I forked out for the E39 Bentley (cough,cough) and there is absolutely no diagnostic info at all on these systems. Only component location and R&R instructions.
The vehicles service records indicate all four wheel sensors were changed once for the previous owner to correct the same symptom and then a day later the ABS control module, $1675.00 worth in all. What diagnostic skills huh, $100/hr for a guessing parts changer.
Any of you guys have diagnostic info or wheel sensor tests? About all I can do now is check sensor impedance and hope one is way different.

[Ross]

Bump

[Brandon J]

Lets look at the commonality not the symptom. So, just one step before looking at the heavy 2 book Bentley. The ABS and DSC rely on the ABS sensors. Perhaps you have a bad ABS sensor connection, a loose ABS sensor, Gunk covering the sensor, or simply a bad ABS sensor. The e39 can store the code for which sensor is triggering the problem with the ABS/DSC. You can also just check. If you check the sensor, remember that it is a magnetic and metal shavings can stick to it and throw it off.

Sometimes the computer just has a bug and as a safety precaution it shuts down the ABS/DSC system. It can go back on. Again, it could also be because its not getting the right info from the ABS sensor. Lastly, check tire pressures are okay.

Good Luck.

[bimmerd00d]

'99 had a very faulty DSC module. It's likely that the problem lies there, but I would pull the wheel sensors first and clean them up, sometimes dirt and grime gets in there. '99-00 failed quite often across the board.

[Ross]

Brandons,
Thanks for the advice. Today was to be my day to fool around with it, as luck would have it the lights have once again extinguished themselves.
All the sensors were replaced once already according to the records, then the module was replaced the next day. I REALLY don't want pay for that module so am hoping the sensor(s) are dirty. I didn't think about tire pressure, I need to check that.