'97 S500 ESP/ABS warning lights fixed with new brake switch, now they're back
 

I replaced the brake light switch to turn off the ESP/ABS warning lights and it worked. Unfortunately they came back on late last night. They'd been off for over a day and were off when I parked the an for an hour. When restarted it they came back on. My mechanic scanned for codes. There are a few pending codes for other things like an O2 sensor, an evap leak and a cam timing solenoid but nothing for the ESP or ABS. Any ideas where to look next?

Off again!
 

The car was in the garage for 24 hours or so. I started it up and the ESP/ABS lights were on but within a minutes or so they went off and stayed off for the 50 miles I drove it. The car will be getting new discs and pads all around as the ones on it are quite worn. Could this have anything to do with these warning lights?

I don't no,maybe wheel sensor is bad or dirty.I know chevys I would disconnect abs computers all the time.Maybe pull asr fuse.

These systems are also sensitive to voltage fluctuations. How is your battery?

Did you replace the switch with a part sourced from the dealer? The aftermarket in this part is full of problematic parts.

Good luck.

Supposedly the battery is less than a year old and the switch is OEM Mercedes. 'Course after asking for help the lights haven't reappeared in about 100 miles of driving so I guess I'll sit on my hands until or if they come back.

The system typically resets by turning the steering wheel lock to lock then to center...your driving may have accomplished the reset....

I got the advice that a small difference in tire pressure can cause this to happen. The car had a set of Michelins on it that had fairly good tread but closer examination revealed a lot of cracks in the sidewalls.

Since I got a good set of Bridgestone Blizzaks with the car, I had them mounted and balanced the day before the lights came back on. I never trust a tire shop's pressures and always check them after I get the car home. I did that between the time the lights came on and the next time I took the car out and they went off again. The pressures were all over the map and all too high, 36-44 psi, versus Mercedes recommended 28 front and rear. Anyway, I set them all at the recommended pressure and the lights, knock on wood, have not come back on.

Unfortunately these continue to come on about once a day. I thought the issue of the different tire pressures had solved the problem but they are all spot on at 28 psi and it continues. It has all new brakes including discs, pads, wear sensors and new calipers and hoses in the rear (they were both sticking).

The brake pedal feels normal when I'm driving the car, but when parked it seems soft and when I push it all the way down I here what sounds like something is "ratcheting." When I do that then turn the car off the lights will either be off when I start it again or will go off shortly after I start driving.

I did replace the brake light switch with an OEM MB part.

They seem to come on at random. I'll be driving along and suddenly they just pop on. My mechanic had scanned the car and while he got several pending codes for other things, there were none for the ABS or ESP.

Any ideas what to look at next, or revisit, thanks.