Constant ABS Light
 

My 1994 E420 has 152,000 miles, and the ABS light is almost constantly on at this point. About 15 months ago, I replaced the brake light switch (thanks to Benzmac) for a similar problem, and the alternator is only 9 months old. Is it likely that one or more of the sensors is bad which is causing the fault? Just trying to narrow down the possibilities for my mechanic before bringing it down, as the ABS system is probably something he doesn't fix everyday. Thanks in advance for your help.

This can be caused by a bad over voltage protection relay.

GregS
'84 300D, 174k
'90 300CE, 163k

Actually, I learned last time through this that the E420 doesn't have the OVP.

Have your ABS Control unit diagnosed, thats what is wrong with mine, just hope it's not that, a New one cost in the $1000's:eek:
btw, i can find a better use for $1000, so i just didn't fix it.

You sure it doesn't have OVP relay? Or is it the case that the OVP relay has nothing to do with the engine management system on that model?

V8 -124s do not have OVP...

Is the ABS chattering at slow speeds? If so, then your ABS sensors are either dirty or shot.

If not, then it might be the ABS controller (expensive) or a low voltage condition. Sounds like your charging system is okay, so you should begin looking at the ABS system itself.

I think that MB dealers have a diagnostic device for ABS, but I could be wrong.

No chattering of any kind. I know that at least one of the front sensors has been changed a while ago, so that leaves either the other front sensor, the rear sensor, or the control unit, right? I think I'll be doing a search for used ABS controllers if it turns out to be the culprit. It's at the shop now, and I should know more tomorrow.