Thanks for the posts thus far.

I own a CLK320 cabriolet with 63,000 miles, which so far is a pleasant experience.
The only problem so far is the check engine light came on after I replaced the air cleaner. I just can't believe it's the O2 sensor yet, the gas cap is tight and I reset with the battery unhook, that lasted about 3 days.

Thanks.

 

Check your MAS you might have disconnected something, a wire, it should be behined the filter on the intake tube to the throttle body, you can't miss it.

 

Thanks,

took it to the MB dealer for fuel filter. They checked the codes and relaced the fuel pressure sensor. Was this BS? Either way the lights out.

 

Yes, it is mostly standard procedure, it does give them the right to charge you for a code check, plus the cost of the fuel filter and installation.

 

fuel pressure sensor?

you got CDI engine.