When I first started driving my car, I didn't install/replace the AC condensor, car ran cold, threw this code. Stuck a peice of cardboard over the rad, car temp normal, no more code.

Guy suggested stuck thermo, took the cardboard off, was 90* out, car still warmed up fine. When the temp came down to 70*, the car started running around 155*, pretty damn cold.

So I'm thinking stuck 'stat. Is this a PITA to replace? The heater core was clogged with shit, so the stat is the likely culprit.