GM Repair Problems? Ask GM Repair Expert Now.
I have seen this a couple of times but it always comes to one of two things, a bad thermostat or a bad coolant temp sensor. Here is how I would diagnose it. You will need a scan tool:
1. Check for a possible DTC P0128 set in the Powertrain Control Module (PCM).
2. With a cold engine, check the engine temperature and air temperature values in the PCM data. The values should match within a few degrees.
3. If the engine temperature sensor value does not appear to be accurate, repair as necessary.
4. If the engine temperature is accurate, replace the thermostat.
Something else you might check:
Has the truck ever had the radiator replaced? I have heard of a couple of instances where the wrong radiator is used and the replacement radiator does not have a surge tank restriction orifice. The essentially makes a huge air pocket in the system which causes the false overheat.
You can check this by looking to see if the coolant is quickly running through the overflow tank when the problem is occurring.
Please let me know if you need additional info.
Let me know if you need any additional help with this.