Yes

 

That was not piling on, just basic questions have been covered so many times it clogs the bandwidth. When somebody does use the SEARCH they get so many results that they get overwhelmed and then b*tch about the SEARCH being useless.

 

Yes I did and that is where I found the thread to copy and paste!

 

The P0128 code reset on its own; analog and digital temp guages are working. I've never experienced an "intermittent" thermostat. Any comments?

 

I'm Sure it will happen again until you change out the thermostat. It's all based on how long the engine takes to reach a given temperature in the computer program. Outside temps and how cold the engine is to start with all play a part it.

 

I did not realize engine codes would reset without any "outside assistance". Maybe the code is still there, but the engine light is no longer illuminated. Kinda defeats the purpose of the check engine light.

 

Some codes will turn off the light if the problem did not return after so many key starts. The code will still be there in memory. Some codes don't turn the light on until the problem happens x amount of times in a row but the code will be there in memory as a pending code.

The pending codes can be helpful when diagnosing drivability problems because they can help lead you to look in a potential problem area.

When you have your codes read at a part store you need to ask them to look and record the pending codes because they are sometimes just ignored.

 

Thanks, Lucky; you've certainly answered my question as to why the light went out. New thermostat should be here on Sat., and I'll install it next week, if the weather warms up a bit.

 

Good luck on replacing it vettman - let us know how it goes. If you want more info, check out the second posting here for another explanation on how the system handles a jammed open thermostat - https://www.chevyhhr.net/forums/problems-service-repairs-42/intermittent-temp-gauge-c-problem-47702/

One key item that some are unaware of, is the last sentence in that second posting above: "The cooler the weather, the more frequently it will occur as it will take the engine even longer to warm up."

 

We've had some cold weather here in NVA, and tomorrow will be even colder. For the past two days, there's been no engine light, the temp guages work fine, as does the heater. The new AC-Delco thermostat arrived in the afternoon mail, so I'm waiting for better weather before beginning the job.