I _just_ bought a new 2012 GL 350. Accellerating off a light, all of a sudden, heard a bunch of noise, and the check engine light goes on. Car runs badly, but still runs.

I pop the hood and I see a large hose leading into the engine on the front - disconnected. The hose appears to be a main hose leading into the engine. Again, it's directly in the front of the engine, leading into the engine, between the radiator and the engine.

I figure I can simply reconnect it.

However, pardon my ignorance, but what exactly does this hose do?

Dealer service is open again on Tuesday, and I can take it in... but if it's such a simple fix, I'd rather just reconnect it and move on!