I have a 2006 Mini Cooper and the service engine soon light has come on. The manual said that means my emission has deteriorated. What does that mean?

You probably just need a new oxygen sensor.

Can you give me an idea of how much something like that runs and should I go to the dealer or can any mechanic put that on a Mini?

You have two O2 sensors. One pre- and one post-cat. The Bosch variety runs $152 each at www.bavauto.com Also, get the tool and do it yourself. If you can remove a bolt, you change your oxygen sensor.

Agree fully with Michael. These can be hard to remove, though. A breaker bar and getting the car high enough for clearance and leverage may be necessary. Put high temperature anti - sieze on the threads of the new ones to prevent future difficulty.

I just got a 2006 mini copper and my engine light is flashing and now the engine is knocking what could be wrong?