Figured I'd get an opinion from the 'sperts over here 
.
My friend's 04 Grand Prix started throwing a P0128 a week or two ago; I've cleared it twice and it's come back each time. I had him do some logging, and got some decent data sets. Not sure what the outside temp was, but the IAT was between 45* & 60*, and while on the highway, the ECT got up to 185 or so and pretty much stayed in that area, until he stopped and got onto slower roads, then it finally got over 190. On another log, when the IAT was in the high 30's, low 40's, ECT hit a max of 178. Since the car is stock, I'd assume it's got a 195* T-Stat, and as such, it should typically run somewhere between 185 & 205 or so while cruising. Correct me if I'm wrong, but isn't the idea of a thermostat to keep the engine in the neighborhood of the thermostat temp regardless of OAT?
I've attached the logs in case anyone cares to take a look.
.My friend's 04 Grand Prix started throwing a P0128 a week or two ago; I've cleared it twice and it's come back each time. I had him do some logging, and got some decent data sets. Not sure what the outside temp was, but the IAT was between 45* & 60*, and while on the highway, the ECT got up to 185 or so and pretty much stayed in that area, until he stopped and got onto slower roads, then it finally got over 190. On another log, when the IAT was in the high 30's, low 40's, ECT hit a max of 178. Since the car is stock, I'd assume it's got a 195* T-Stat, and as such, it should typically run somewhere between 185 & 205 or so while cruising. Correct me if I'm wrong, but isn't the idea of a thermostat to keep the engine in the neighborhood of the thermostat temp regardless of OAT?
I've attached the logs in case anyone cares to take a look.
Last edited: