I have a 2004 C320. my "check gas cap" and "check engine" lights keep going on, even after I've tightened the gas cap. Is there a problem; what is the solution?
Thanks!

 

if you are sure the cap is on correctly- you might just need a new cap. the vent that's built into the cap may no longer be working creating a malfunction code.

i diagnosed the same problem for a neighbor of mine on his ford ranger a couple months back. he was getting some sort of emissions and vacuum code.

 

It usually takes a while, some start/stop/drive cycles for the light to go out. The error message actually said "Check Gas Cap"??