Dino Gravessi

ISSUE: There's a LOT of information on the internet about the "Engine Hot / AC turned off" message that scares everyone when it pops up the first time. If the warning displays and the engine is not hot (one radiator hose kinda hot but the other is cold or barely warm) it's because the engine has not gotten up to operating temp in a set amount of time, usually around ten minute. Sometimes the warning will be accompanied by a P0128 code, “Coolant Thermostat Temperature Below Regulating Temperature”. This is proof that it's not hot but actually too cold. The issue occurs more often when the ambient temp is colder (winter). SOLUTION: You MUST have a 195deg thermostat in the system. That's it. The valve will stay closed longer and allow the engine to warm up to operating temp and you won't get a warning. HEY GM! The fact that there isn't a warning message for "Engine too cold" and instead "Engine Hot / AC turned off" gets used instead is completely unacceptable. As an engineer I would be embarrassed to be part of the team who designed this system.

Just following up on Richard's post about the 195 thermostat. This is the solution! If a lower temp thermostat is used it takes too long for the engine to warm up and the computer sees it as a problem, but it looks like there is no error message for "Engine cold" and it uses "Engine Hot / AC turned off" instead. Very misleading and GM should fix this. It takes about ten minutes after cold start for the error message to display and will occur more often with colder ambient temperatures (winter). You MUST use a 195deg thermostat.