ironheadbro

I have a 2006 HHR that has an intermittent problem with the engine temp sensor. Sometimes it is operational and the cabin temp gauge works, (at which point so does my a/c and remote start), but when the gauge isn't activated/working, the a/c and remote doesn't either. I know from reading the other posts that a bad sensor will cause these other secondary issues and I'm ready to change out the sensor,,, if that's for sure the problem. Here's my question. Is it typical for this engine temp sensor to cause this intermittent problem or is there a switch/relay/connector upstream that may be the culprit? Additionally, my thermostat is working correctly as I have heat in the cabin when the gauge isn't working.
Thanks
Ironheadbro

donbrew

A: check your coolant level!!!!!!!
B: check your t-stat.

It is not usually the sensor, more than likely you have never looked at the coolant level in the reservoir (most people don't). Or, the the t-stat has gone bad. As has been covered the "temp" reading is dumb, meaning it does not know what media is reading ie; fluid, metal, AIR.

If the plastic bottle has enough coolant in it, then check the tubing to the radiator. Then when the engine is COLD open the pressure cap and check the level at that point, it should be full. After that, go get some Dex-Cool and a t-stat and schedule a half day of dealing with the car, there is lot's of standing around time, so find other small things to work on!.

ironheadbro

I did happen to check the coolant and it's right up there at the top. I just checked the tubing line to the rad and that is also unobstructed. The T-stat is working fine,,,,, I get plenty of heat coming out of my heater on these now cold mornings in Michigan.

ChevyMgr

thermostat would be the most likely, heat or not in the cabin.

whopper

Agreed - thermostat!!!!

What is happening is the thermostat is jammed in an open position. This makes the engine slow to warm up. The slow warm-up is detected and the computer disables the a/c, blanks out the digital temp display with "----", disables the analog temp gauge, and will trip the CEL with a p0128 code. all of those symptoms will be intermittent - much dependent on the ambient outside temperature - ie: problem likely will be more likely to show up on a cool day.

The fact that the heater still puts out heat is irrelevant.

843de

X 3.....Thermostat.

ironheadbro

Got it. Mr. Thermostat is getting a new home,,

TiggersHHR

On my way back home from Northern Indiana my 07 (little over 68,000 miles on it) did basically what Whopper said - Analog display quit working and digital showed "----" - except mine never cleared when the weather warmed up. I figured it was going to be the coolant sensor or thermostat - since it is still under factory warranty I took it in to my local dealer. They put in a new sensor and thermostat, but still displays did not work. The ended up replacing the ECM (Engine Control Module) - they stated that there was a communication problem in the ECM. Don't know and don't care - just as long as it is working.

whopper

Good deal man. One of the tips for diagnosing the thermostat as the problem, is to watch the digital read-out as it is warming up (of course it has to be in working display mode, which should be resetable by disconnecting the NEG post on the battery for a minute or two). As it warms up you will see the temperature increase slowly, then go "----". With mine, when it was cold outside - maybe 45F???? - it just would not warm up fast enough and would trigger the "----" fairly consistant and fairly quickly. The warmer it was outside, the less inclined it was to "----" out on me.

Will keep the ECM issue in mind. Glad it's all working for you.

TiggersHHR

Well it looks like my HHR is going back in. I don't know if it was the parts they put in it or if they did something else - but now my HHR is running about 20 degrees colder. It normally ran at 196 to 205 - now it's 178 to 185.