MH,

I had an ABS issue with my 87 SDL. I'm guessing that Mercedes uses similar parts and technologies across the different size cars, and mine was the same year as yours.

After a little carefull tracing I found the wires from the ABS sensors come up into the engine compartment. There was a connector, then the wire proceeded to the ABS unit. My driver side connector was near the fuse box, and passenger side was in front of the washer tank. There were a pair of wires coming from the front wheels. 1 wire had a flat connector for the brake pad wear sensor and other a round connector for the ABS. Measuring the ABS I found 1 side open and 1 side at 1300 ohms. I had bought a pair of used sensors and they both measured about 1300 ohms as well. Replaced the open one and it was fixed.

Another common reason for the abs malfunction could be dirty sensors. They can be removed fairly easily from the front hubs. I sprayed some brake cleaner in the holes and turned the rotor to clean out the "teeth".

Good luck.
Chuck