[megladon]

Hey folks,
New to the sight. I've owned my 02 w/the 2.7l for two years now and have had some overheating issues with it since I bought it. When first purchased one of the radiator fans wasn't working and caused some overheating problems. After it was replaced, it was better, but not 100%. I live in the desert southwest where we hit 115 degrees without batting an eye. When I run the A/C and push the car kind of hard (usually when I'm late for work) it understandably starts to get hot, but will cool back down if I either back off the gas pedal or turn off the A/C. When I get to where I'm going I let it idle for a few minutes before shutting it down. When I got off work last night, the engine light came on. I pulled a P0128 code which, according to allpar.com, is Coolant Thermostat. OK....what about it? The engine stayed in the normal temp range, about a needle width below the half mark. It ran fine the rest of the 35 miles home. Does this mean the thermostat needs to be replaced? Is it stuck open? Has it been damaged some how? Thanks for any input!!

 

[Ronbo]

P0128-Thermostat Rationality

The PCM predicts a coolant temperature value that it will compare to the actual coolant temperature. If the two coolant temperature values are not within 10 degrees C of each other an error is detected.

Possible Causes:
Coolant level
Thermostat

That's all the Powertrain diagnostics manual indicates for that code. If your coolant level is good, then it looks like it's time to change the thermostat. My money is on the thermostat not working right. Might be some spooge broke loose from the radiator or elsewhere preventing the thermostat from opening or closing properly. Probably a good time for a flush/coolant change along with the thermostat.