I had the oil changed at Jiffy Lube on my 96 E320 and they also performed an emissions cleaning service. the emissions cleaning consisted of removing a vacume hose and spraying some kind of aerosol cleaner into it. The manager said my check engine light may come on and to bring it back after one tank of gas and they would reset the light. I did that but the light keeps coming on. It is a stored code 66 (regeneration switch over valve). I've had it reset at my (non dealer) mercedes specialist mechanic twice already. He tells me that it could be a short in the wiring and wants to replace the wiring harness for around $1200+. He claims that the wiring is a problem in these cars, it gets dry and brittle with age and cracks causing shorts. THIS CAR IS ONLY 7 YEARS OLD! btw, the car runs fine, this light just keeps driving me crazy. sorry for the long post. Any Ideas?