CLK Radiator Oil Pressure Problem Solved

Sounds familiar. I had similar issues with my CLK's transmission a while back. Was the radiator coolant low? Check for leaks around the radiator hoses and the radiator itself. Sometimes a small coolant leak can cause car overheating and weird electrical issues later, throwing off the TCU.

Coolant level is fine. No visible coolant leak detected. Are you suggesting a minor, undetected radiator coolant leak could cause radiator oil pressure issues and transmission problems?

Yeah, that's what happened to me. It was a hairline crack in the radiator. I didn't see it at first. The glycol contamination messed with the electricals. Best bet is to have a shop pressure test the cooling system to check for leaks. Could be a bad sensor too, but start with the easy stuff.

Confirmed. Took it to the workshop. They found a defective radiator oil pressure sensor cable connection. Replaced it. Error gone, transmission shifts normally. Total cost 95€. Thanks for the pointer.