I'm new here so I can only give you my experience.
I had a 87 560SEL and the ABS light was on too. In my case where the ABS unit is I took off the black cover and took out one of the fuses and the light went off. I'm not sure if your car has the same unit, but it's worth a look.
From reading these threads I've heard many people say to check the connections at the wheel and make sure they aren't dirty or broken.