So my coolant gauge stop working the other day, which wasn't s shock to me because this has happened to me several times before, started about 6 months ago, and apparently is common with HHR's. I've had my HHR a year and 1 month. Usually the coolant gauge would work again after about 5 to 10mins. But this time not so. After 10mins the Check Engine light came, so now I'm like s@#. The HHR was fine, drove home fine, I felt nothing in the engine that was different. I was hoping I wasn't one of those with the misfire issue. So I stopped at the AutoZone where I work and grabbed the code scanner. (Not wasting my time at the dealer to pull a ECM code. The first code reader just said link error. Then I tried the newer one we just got in. It linked saw 2 codes; great I'm thinking got the codes, both the same code. P0128 - Coolant Temperature - Below Thermostat Regulating Temperature. Basically, it's not getting warm enough. Which was true. I had the heater on burn, and it was a mild warm, I have had it so hot in there, my skin felt sunburned. Of course like others, the DIC said --- under Coolant Temp, no surprise. So I cleared the code, when I did that, the gauge starting working, Hummm. Checked coolant, overflow was low, but when I squeezed the lower hose, coolant pushed back through the radiator through the upper hose. So I topped off the coolant bottle. Drive my baby for about an hour 30 on the highway 30 on the street. The heat got hotter checked DIC and coolant level was 183 to 217, at which point the fan kicked, and it cooled real fast to 185, and would not go any higher then 211 from the point on, which is where it usually stays when I am in traffic on a normal Cali day in Spring. The gauge stayed on the whole time, and no check engine light. Then I remember another side effect of the coolant gauge not working is loosing the A/C. So I turned it on, full blast, with in not even a min gauge went down, DIC said --- and A/C was no more. Damn! And a bunch of other "French" words. So now she is at the dealer, since the light had not come back on yet, they said they’d see if they could pull a code. They're for sure going to check the gauge issue, the Service Adviser suspected a cooling system issue. But he's not the tech so who knows. Soon as I do I'll post it. Good thing my local dealer is pretty good and it's under warranty. It just sucks not having my baby.

 

You might refer your dealer to TSB 06-06-02-013A

Not saying this is the problem...but sounds like it.

 

Had the same thing happen to mine off and on for months, turned out the thermostat was stuck open (better open than closed!). The dealer put a new one on and haven't had a problem since...

 

So it's been a full week since I got my HHR back. Seems the issue with the Check Engine light was the Thermostat was stuck open. Which was a good thing, so they replaced that. The coolant gauge and A/C not working was because the battery run down protection thought the battery had drained before , and that was causing the PCM to shut the gauge off. Sound weird to me. Any how they loaded some update to the PCM, and they checked some wire I guess that's close to the engine block in the rear, what wire I am not sure, on the invoice it said brown wire checked for cracks and if touching the engine block. Apparently this has been a issue with some HHR as it states the tech called GM to verify. Anyhow, runs like a champ (did before that anyway) and I got A/C just in time for summer and my gauge is working.

 

Thanks for the update.

 

It happened to my car today

 

Couple days previous to what is being described here I got a message saying my gas cap was loose. When I got home I opened it up... it looked secure. So I opened and closed it. Restarted my car and it went away.

Then today I have the Engine light pop on and stay on. I start scrolling through my DIC and notice that my Coolant Temp is reading - - - like you mention. My coolant's tempature is not reading anything on my main display either. I figure I may as well see if it needs coolant and get some of that 50/50 DEXCOOL and top it off. Only uses about a quarter of the gallon before its full. Engine is warm but not hot... so I figure that isn't it.

And that is about as far as I've gotten...

I am not as savvy as the original poster... what is my next logical step?

 

More than likely it is the thermostat stuck open. Won't kill the car but will make your gas mileage suck. Should have it looked at by a professional.

 

Does anyone know what the code is for this error? I'm having the same issue and am hoping it is not my thermostat stuck open!

 

DTC P0128 is "Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature".

You can get a DTC scan free at many auto parts stores. I know Autozone does it around my area.

Hope this helps.