Suddenly having the same issue on my 1997 E320. In the past it was related to a low-voltage condition. I resolved by cleaning the corroded ground cable in the battery compartment.

This time it's different because I can shut the car off and start it right back up and the light goes out (before, the car wouldn't turn over due to low battery).

Question - can replacing the brake switch help on my car? I see only the 98-03 cars referenced in post 17 above.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280