AlexNguyen1

Hi guys,

Need some help here, please. Just changed my thermostat and radiator to Mishimoto due to OE failure. Now I'm throwin' a CEL code P0128 which is the thermostat overcooling. How do I fix this?

I double-checked all my work. Sensors are all reconnected. Both fans reconnected and working. Hoses reconnected, no leaking. Burped the system for 30 mins, no more air bubbles. Engine temps run cooler than normal, but that's expected with Mishi X-Line. Normal engine temp is about 4-5 bars

outeiroj

did you install an oem thermostat or did you put in a cooler temp one? not uncommon of an issue for cooler temp thermostats to cause this issue on modern fuel injected vehicles.

AlexNguyen1

I installed a Mishimoto thermostat as well. I cleared the CEL, but it came back. I haven't checked the code again, but I'm assuming it's the same P0128.

I think to fix the CEL I might have to change the sensor on the radiator to Mishimoto also, but I want to be sure before I spend another $50. Everything is "supposed" to work fine with the OEM sensor.

outeiroj

oem thermostat opens at 172.4 degrees the mishimoto opens at 154.4 degrees. Put in an oem thermostat, and it will fix the problem. The mishimoto is causing the engine to never get up to normal operating temp because its flowing past the thermostat too early which on fuel injected cars causes issue with fueling. Lower temp thermostats are not typically designed for cars that don't see excessive heat.