Could be the sensor or it's wiring.

 

I never saw that at all about the T-stats,just the simple "replace them".
NOW that I have the paperwork firemangeorge,I can confirm Oldblue nailed it. Paperwork shows a P128 code.
And as far as the Dexcool,what I drained in a pan I put back in and only needed to add almost a pint of water when I finished.

So,looks like I'm doing this all over again...

 

The search engine here isn't the best. The default 'Threads' sorts by the date/time stamp of the most recent post in a thread that has the search criteria in it somewhere. If you change to 'all' you get a search powered by google, sorted by relevance, which usually gives you better results.

That being said, the newer the advice, the more accurate it should be. The older posts are often closer to guesses, as there wasn't as much hard facts yet on a new HHR.

 

That's how I start off,with Google and click on the ones from the forum...

Since I know what I'm in for with the thermostat R/R,the second time around should be a breeze...