First time this happened to our 2002 GMC 2500 4wd, we were told to add coolant...which we did, although it seemd full, and the truck ran just fine afterwards. For no apparent reason this has happened a multitude of times since then and at different times. Of course we did what we were told and added coolant to an already full system which up until lately worked every time. Now it seems it was more shutting the truck off and on that had to do with resetting this, since that's what seems to do the trick now. We took it to a dealership and a local mechanic who both came up with some codes ( PO 120 TP or APPsensor circuit 1 and PO 220 for circuit 2, PO 332 knock sensor, P1516 something to do w/ throttle mod., P2135 TP sensor 1-2), and were told these codes were not on their list??? They are s'pose to be digging into it some more for us, meanwhile we drive around never knowing when it will re-occur...and frustrated. Anyone make any sense of this? I have read where a loose ground wire fixed this same problem? Also, where the gas cap, fuel pump, and throttle quad was the culprit... so, it appears to be a common problem with no common solution. Seems like a good idea as far as protecting the engine from overheating, but I will probably avoid it in the future if possible.