Have an 08 MCS. For the most part the car runs really well and goes down the road with the best of them. Been having trouble with a PO128 code which we all know point to a stuck "open" thermostat. Thinking I got a bad part from(3 of them) Napa Auto Parts, purchased a new OEM thermostat with housing from Pelican Parts. Still get the same code. Finally gave up and took the car to the local German car service, a guy I have used before and have confidence in, and he came to the conclusion that the thermostat was bad again. I am gonna change the thing one more time but I am having trouble believing that in 1000 miles 4 of these units could go bad. I need any help or ideas as to what is causing this issue.

 

Sounds like a connector or wiring issue to me. The probability of even two bad parts in a row is very low, 4 just about impossible.

 

Still looking for advise. Bump