BERNS

Hello All,

I noticed that my temp gauge was flat and I scanned my car and an ECT code was present and stated pending.

I decided to clear the code and once cleared the gauge started working.

Is this normal? Could it be thermostat starting to go out.

I am asking cause I was reading posts but nothing mentioned anything like my issue.

Oldblue

It could be the thermostat, how old is your Dexcool (coolant), it has a 5 year life.
If it hasn’t been changed in awhile or you’ve never changed it since you bought the car change the thermostat and the Dexcool.
Just in case here’s the how to

https://www.chevyhhr.net/forums/how-...l-p0128-24493/

donbrew

As soon as the computer senses the temp is not where it is supposed to be at the right time the code and the display will come back, and your A/C will stop.

Your case is exactly the same as all of those others, assuming you mean P0128.

Cat Man HHR

X2 on this.

Oldblue

And let me elaborate, by thermostat, I mean the correct AC Delco 131-158 180 degree thermostat.
And proper 50/50 mix Dexcool.

BERNS

Thanks to all. I ended up replacing the t-stat.
Previous owner is a co-worker so I asked him and he said he had changed it about 10k miles ago. Part looked a bit different than the AC Delco as it was a Napa brand stat.

I bought the AC Delco part and installed and put together in 20 min maybe less. It took longer for the car to circulate the coolant and fans to kick on.

Drove it for a solid hr including sitting at a del taco drive thru for 20 min and never overheated or flat temp gauge.

Daily is back on the road and back to enjoying after sitting for a week driving my weekend car due to no time and being dark by the time I got back from work.

All in all, this is as easy as replacing the t-stat on my old Caprice with 350 V8, that is cause I had all the right tools at hand.

This is an awesome forum.

donbrew

To explain for the umpteenth time; the code is because the coolant does not heat up FAST ENOUGH. It has nothing to do with over heating. The code causes the flat lining, not the other way around. It is more likely to occur in cool weather and when the coolant temp is lower than 190F.

BERNS

Thanks. I did not have an issue with overheating.

I was just mentioning that all went well, no code and no overheating from the stat not opening.

Everything works as it should.

donbrew

The p0128 code comes from the t-stat opening too soon or being stuck open.

Contrary to popular beliefs the t-stat has little to do with over heating. It's job is to keep the temp UP.

BERNS

Thanks. Makes sense.

Note that the reason I thought it was stuck closed was that my fans were running continuously on start up.