2008 C300 4Matic with 68,000 miles
Just got this car and after a few miles the CEL came on. At first there were no codes and at least once the CEL cleared on its own. I cleared the CEL a few times but it would come back after driving for awhile (not every time it was run). Now the CEL is on and it is showing P0016 and P0128 codes. I cleared them once and it is back on with the same codes.

It appears that the thermostat has been problematic for some of these vehicles, but I couldn't find any that threw both of these codes together. Does anyone have an opinion on this? I don't mind replacing the thermostat if that is what it takes, but don't want to do it unnecessarily.

 

Thermostat won't make car not start

 

Huh? What are you chaps talking about?

 

I should have also said that the car runs and starts fine with no noticeable problems. Running temperature is slightly above 80 C.

 

Replace the thermostat & variable cam timing magnets. Do all 4 while you are about it. They have been redesigned.

Good luck!

 

The CEL has been on for about a week. This afternoon, the CEL went off while driving around (codes were not cleared by my code reader). Would this point to either the thermostat or variable cam timing magnets as the potential culprit? I don't mind replacing parts, but hate to replace items that are not needed.

 

The thermostat starts opening at approx 87 deg C & should be fully open by 90. So your car should run at approx 90 degrees. If it runs colder than that after warm up then replace the thermostat. The cam magnets are a known problem. There is even a warning that comes up on a dealer's Star telling them to replace them with the newer magnet design.

If you want to make sure before doing anything then cancel the stored codes with an OBDII scanner. Drive the car for a few days and check again to see if it is storing new codes. Remember a CEL only triggers once a threshold is reached of e.g. 500 misfire codes or 100 cam timing codes or whatever.