So I changed my hoses, flushed the radiator, and put in a Mishimoto Racing Thermostat. Car has driven like a dream for a week, and now the Service Engine Light has come on; the code pulled at Autozone is P0128.

I really liked the way the car is driving...am I doing harm to the car? Can I make the light go away?!


Thanks!

 

The engine is running cooler, but that code is for coolant temp below specifications. I know on my last car, which was high compression and supercharged, i ran a drilled thermostat to keep a constant flow of coolant but i had to get that code programmed out of my PCM when i had my tune done to keep the CEL from popping up. You're not hurting the car, its just taking longer for the car to heat up to operating temperature so the car thinks something is wrong. Depending on where you live, that could be problematic, especially in really cold climates where the engine wont get up to proper operating temperatures...and also your heater in the car wont work as well. Unless you are tracking your car or doing a lot of high speed runs, or running a high boost/high horsepower setup, you really have no need for a "racing" thermostat. Switch back to an oem replacement and you'll be back to normal.

 

I live in Texas, and am careful to warm the engine for a couple of mins before driving in the morning. When you say you got the code programmed out of your PCM when you had a tune, do you mean a tune like Uprev/Osiris? Cause I'm getting that done in a couple of weeks...it'd be perfect if I could ask them to get rid of the code.

Thanks!

 

It was a GM car that i had done too. Im not sure if it can be done on these cars. The thermostat isnt allowing your car to warm up as quick as the computer thinks it should. The code will continue to come on until you swap it for a normal thermostat, or have it programmed out the computer, if it can be. If it can't then the code will continue to come on.

 

I would swap back to the OEM thermostat unless you have a need to run that thermostat.
"Racing" parts dont always = better performance for daily driven cars, some are actually detrimantal to performance.

 

when running cooler the only thing that you will see in our cars is that unless you are warmed up and stay steady at the normal operating temperature you will burn a lot more fuel and you won't be able to use the heater very much

 

+1 unless you're tracking it's useless. Just go back to stock..

 

strangest thing ever, put in a new y-pipe and the CEL light has disappeared!!?

I don't want to get rid of it, because the car felt SOO much better once it was on. I don't think the change was simply because of new hoses and radiator coolant (did all three together). if I run the car till the temp gauge is in the middle, am I still burning more fuel?