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Old 02-19-2013, 05:58 AM
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Flybot Flybot is offline
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Location: Louisville, Ky
Join Date: Aug 2009
Posts: 1,007
Mein Auto: '98 528
One month followup on the intermittant ABS/ASC light.

I was initially getting the two mentioned lights and they would go out either at random, or sometimes if I turned the wheel from lock to lock. This degraded in to the transmission not automatically shifting in to 3 or 4. If this happens, you can manually shift up by clicking the shifter from D to 3 and back to D. Downshifting is still automatic. Anyway, I thought initially it was the steering angle sensor because it could sometimes get it to go away by turning the wheel. I wanted to do the diode check on the wheel speed sensors using Bluebees thread but I have the older ABS System ('98 528) and the pin outs dont match up. I found this thread with the pin outs for the older ABS system:

Anyway, I changed out the left front sensor, which was literally crumbling apart. When tested, I got zero volts on the diode test and 3k ohms. It was supposd to be .5-2M ohms, according to the M3 thread. I cut the cable of the old sensor to do some further investigation and found that it had a small cut in the outer black insulation. The inner yellow/red wires were crumbling apart just touching them, and the copper was actually green from corrosion.

So as with all intermittent issues, it is fixed- until it isnt. The left front sensor was without a doubt bad, and I havnt had any errors since changing it out. I still dont see how the one sensor went from ABS/ASC error to then later include the transmission. Im keeping my fingers crossed.

This wheel speed sensor clearly gave its all and will receive full honors as it is laid to rest in the trash can.

Wires corroded 6" from the end of the sensor cable?

Crappy pic showing the wheel sensor and not showing the two bolt holes for attachment because they crumbled apart when removed??

Last edited by Flybot; 02-19-2013 at 01:12 PM.
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