1998 528i - possible ECU problem

Raulg · 03-14-2010, 06:57 PM

I have a 1998 528i, automatic.
A few weeks ago the ASC light on the dash came on and has stayed on. I noticed that the brakes intended to slow down a slipping wheel are not working.
A couple of weeks later, the transmission would not upshift from 2nd gear. I noticed if I manually shifted to 3 and back to D it would then shift. This condition lasted 1 day. I can't recall what type of weather we had at the time.
It rained heavy at times this weekend and the shifting problem returned. It has been two days and counting. While driving today at 50 mph or so, the speedometer dropped to 0 mph and has stayed there.
Is this an indication that the ECU is bad? could it be due to water? Where is it located? Could it be something else? I would appreciate any help. Thank you. Raul

Raulg · 03-17-2010, 01:41 PM

Update: I had read on the 3-series threads about water damaging the ECUs. I took the cabin air filter out (engine bay passenger side) and removed the black plastic cover underneath. Turns out that this car has 2 computer boards. They were dry and the wiring appeared to be in good shape. No brown-outs.
I called the shop and asked if the ECU could be tested off of the car. I was told that they needed to see the car and check other items that can cause the problems.
I contacted the shop today. There are 3 speed sensors (rear wheels and front driver's) that produce no signal. The tech advised to replace all four speed sensors. I agreed. Rears $135, fronts $150 plus labor.
The possible down side is that the shorted-out speed sensors may have damaged the ABS module. The tech will know once the sensors are replaced.
Let's hope my ABS has survived.
R.G.