I'm having the same problem with my 1998 S420. I actually had both the ABS and ASR lights come on and stay on, even after engine restart, a few months ago. I had the brake light switch replaced, and that fixed it for a while, but recently the problem has returned.

Now, the ABS and ASR lights come on most often when I am just feathering the brake pedal, such as in stop and go traffic on the freeway, when I feather the brake and then let off. Or, also when I'm parking it happens a lot. Now, however, the lights are reset after engine restart.

Is it possible that I just need to get another brake light switch?

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Mark S.
Seattle

1998 Mercedes S420, Smoke Silver, 138K