From what I've read that deals with how fast the water temp comes up to keep the ECM happy when starting cold. If that parameter isn't met you will get that code.
Have a lot of miles on the car? Change the thermostat and more than likely change the anti-freeze.
Get the Delco T-Stat only. This p/n may have been updated.
https://www.gmpartsdirect.com/oem-pa...bC1sNC1nYXM%3D

Sitting at about 166k. Coolant was last changed at about 150k. Im assuming the thermostat is on its last legs, however pretty much everyone on here has the --- readout and no gauge. Maybe its just a matter of time before it happens here.

Was a Delco part installed when the coolant was changed? Or did someone just do drain/refill?

It was just a drain/refill. I had it done same time that I had a bunch of little maintenance things done before traveling cross country. Thinking back I should've had them do the thermostat just as a preventative, but it didn't cross my mind.

Then do it and see what happens.
Bet you the code goes away.

X 2!!

My money is on the T-Stat and bleeding the air out if the system.

166F is a lot more than 10 degrees cooler! It should be above 180F.
It could be the temp sensor, but you can visually inspect the t-stat before spending the money.

166K is the miles on the vehicle.

Just woke up from nap:bow: