My -88 745 has started to light the ABS lamp when the car starts rolling. It is unlit when the engine is started. I have measured on both front wheel sensors with a DMM. Left ca 500mVAC and right ca 400mVAC when I rotate the wheels (car raised). What next to check? Relays? Hidden Fuses?
TIA!

Hi there.if your car has a diagnostic socket try to pull the ABS codes (socket A position 3),if not clean both front sensors and reluctor wheels.also check the wiring for the sensor at the rear of the differential.and check for corrosion at the battery + cable,before you replace any relay.FAQ has lot of valuable info for ABS system.good luck and have a good day.charles.

Thank you for your answer!

I have already looked at the FAQ but I didn't find any in my opinion more detailed troubleshooting tips. I guess that since I get a fairly high(?) reading from the front sensors, they are OK. Secondly, since the speedometer works, the rear sensor should be up and running, or not?
Unfortunately, there is no contact in hole no. 3 in the diagnostics box. Therefore, I can't get any diagnostics information there.

You said that I should check for corrosion at the battery + cable. why? It is OK, alright, but do you mean that a voltage drop there could affect the ABS? In that case, the ground wires should be checked as well, right?