Take Webmaster's word and read the brake service article in the DIY section. However, your brake system might be different than the ones in the article (95 and 98 E class). I just replaced the front brake pads for my 94' C280. Let me know if you have a similar model. Actually I found it's much easier to replace brake pads for the C class (Single piston, floating type). You don't need to reset anything. Once you replace the bad sensor, the light in the dash will go away. Do use Mercedes OE pads and apply brake pad paste on the back and side of the pads.

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Harry (94 C280)