This is in all likelihood your air pump/smog pump, which is a device that injects air into the exhaust stream before the exhaust moves through the catalytic converter in order to lessen the emissions that come from the rich fuel mixture on a cold start. That is what the code corresponds to on my C280.

As for fixing it, you're probably going to have to replace the pump. I really don't know if this is DIY on an W220. I've been living just fine without fixing mine, coming up on three years now. I just reset my light every so often to make sure there aren't any additional codes hiding in there. The part only operates for the first 45-60 seconds after a cold start, anyways.

Jonathan

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Jonathan

2011 Mazda2
2000 E320 4Matic Wagon
1994 C280 (retired)