You were not wrong, you had to be sure and checked everything out before you could be sure.
now you know what the problem is and you confirmed it wasn’t the CTS.

 

At least tried to do some testing, and actual diagnosis, instead of just replacing a bunch of parts!

 

Got my thermostat today, You guys weren't exaggerating how easy it is to replace. 10 minutes tops, a very small amount of coolant loss, and a nick on my thumb (no idea what got me, but it did) I'd wager it would be more work to change the sensor. As you can see in the pic, the rubber o ring has intruded into the thermostat, preventing it from sealing. This also was not a GM thermostat, it was a Standard.

 

Gee, I was wrong; I said a skinned knuckle not a cut thumb.
Probably one of the hose clamps got you.

 

Just curious why my driving temp has always been 197-200 over the last few years, I would think that an open thermostat would have given me a temp closer to 180 or less. I am guessing the thermostat must have failed much more recently. I am expecting to see a failure similar to the picture above.

 

It failed when the CEL lit up.

 

Jim,
The ONLY time I cut myself is when I am working on my car.
Go figure.

 

Jobs not done till there bloody knuckles! You can’t get calluses if you wear gloves!

 

OK so I paid my dues (again) and spilled some blood.... The old thermostat was messed up with the rubber inside (see picture) and the only brand name I could find was STC . After getting it apart, we couldn't get the thermostat to come out of the block. Ended up getting a long screwdriver in there and popping it out. New one went in fine, but it was a chore getting the bolts back in place. Big hands ya know... It did dump quite a bit of coolant so we refilled and test drove it. After about 5 min it was up to 180, then dropped to 178, then back to 182.. so I would guess it is working correctly now. It is resting comfortably with pass side front wheel on the cueb to help the air bubble escape once it cools down. Then we will refill. (see I do pay attention)



Again, you guys were right and hopefully it is done. This is the thermostat that was in there since I bought it about 3 years ago.(the truck, not the thermostat)

 

Yep, that rubber ring is the problem. But it’s fixed now, check and top up the coolant tomorrow morning and again on Thursday and Friday. Now kick back , crank up those tunes and enjoy the warm air from the heater!