I brought a 2003 mazda protege5 2.0l 5 speed. Check engine light came on, code p0117 Coolant temperature sensor low circuit. The temp gauge start to rise to the H. Check fans, fans comes on between 190-205° Replace coolant temp sensor, replace thermostat, replace coolant temperature connector. Code still didn't go away. So now I took my volt meter ohm out the violet/Yellow wire that' going to my pcm, it' 0 out. Ohm out the ground, the ground needed some work. Replace the grounds wire from the battery to frames. Light still on. So now I'm guessing is my PCM is bad? If so can I upgrade to an mp3 pcm. I need more info on pcm swap.

 

Did you drain and flush the system and replace the coolant?

Use a non-contact IR thermometer to measure the temp at the radiator inlet and thermostat housing.

Did you reset the codes after the other part swaps?