H2 hummer 2003. Check engine light came on. Temp gauge says 178 degrees. Codes are P0128 coolant temp below regulating temp and P0229 throttle/pedal position sensor / switch C Circuit intermittent. I changed thermostat and temp still running about 178. I believe my temp usually s/b at 210. Thinking about changing coolant sensor next. Where it it located? Any one have these codes before and what was the solution. Thanks.

 

Btw no performance issues that I've noticed.

 

P0128 most times sets due to t-stat stuck open. Takes too long for engine to reach operating temp as compared to the intake air temp sensor and length of engine run time. So first thing I would check would be for coolant flow prior to engine reaching operating temp. P0229 is not a code in manual. P0220 maybe?

 

So how do I check coolant flow if it is a sealed system? P0229 is a code. P0229 OBD-II Trouble Code: Throttle/Pedal Position Sensor/Switch C Circuit Intermittent. There a description on the Internet. My guess is this code triggered bc low temp reading but not sure yet. Don't have any of the symptoms of this code.

 

Start the engine cold and as it warms up monitor the rad hose temp downstream of the t-stat. Should stay relatively cool till t-stat opens. If it gradually warms with engine temp that would indicate coolant flowing past t-stat. P0229 is a generic obd2 code yes, but not one that sets in an h2. If your using a code reader it may be giving that code cause its programmed with generic obd2 in mind. Try a tech 2 or a good snap on scanner and see what it says.

 

Thanks HumTech. I did use and inferred temp gauge on t-stat housing and the hose near by and was around 170. Temp at gauge now reads about 205ish. Thinking I'm good for now unless I throw a code again. Thanks again.

 

Did you use a 195 degree thermostat?

 

Bought what Advance Auto said was for the vehicle. Internet says it 186 degree. Weird that at the housing and also hose near by I get 170 reading and gauge in car says 205 ( it was reading about 178 when I got the codes). Guessing the sensors in the head reading on the engine is hotter...closer to the combustion and that sensor operates the dash gauge. Thinking I'm good for now.