The P0118 code means that the engine control module (ECM) has detected a voltage signal that’s too high from the engine coolant temperature (ECT) sensor (below). In practical terms, the ECM believes ...

Q: My 1999 Pontiac Sunfire coupe is doing something something I can't easily explain. The car has 240,000 km on it and it has the stock engine, although I think I bought it with a K filter charger.

It's most likely to be an engine sensor, or a wiring connection associated with one, that's the problem. Unfortunately, intermittent problems are hard to detect, because they rarely occur when the ...