OK, this one is a long one, and a toughy…
Last year I drove my 2006 F150 from Vancouver, BC down to Moab, UT in April. We stayed overnight at a rest area in Idaho (near Twin Falls). When we left the rest area in the morning, we got 10 or so miles down the road and the chime went off, the temp guage spiked to hot and the LCD displayed said “check gauges”. I immediately pulled over opened the hood and started to check for any kind of overtemp issue. After 5 mins of hunting around, I found nothing, got back in the truck and everything returned to normal. I drove down to Moab, then Fruita and finally Sedonda, without any issues. I did not notice the CEL - it could have been on, but I was focused on the temp guage.
On driving back home, we drove the same route. This time we had been driving for about 4 hours, and in the exact same location in Idaho, I again, got the chime, spiked temp gauge and “check guages” light. Again, I pulled over, checked everything - but no temp issues. 5 mins later, started the truck everything was fine. Again, I did not notice the CEL. Drove it all the way back home with no issues. Drove it all year towing the trailer with no issues.
This year, we drove down to Palm Springs, then to Pheonix, again towing the trailer. No issues going down, BUT, after a couple of hours driving, we came near Twin Falls again, and AGAIN: the chime, spiked temp gauge and “check guages” light - BUT this time I noticed the CEL on, and it was stumbling. This year I brough a code reader with me. So pulled over, plugged in the code reader and Found code P1299 Cylinder Head Overtemp. Interesting. Well I gave it a rest for a few mins, cleared the codes, started in back up and again, made it back home with no issues.
My trailer weight is well within the towing limits of the truck. I drive slowly and carefully - I want to keep my truck for a long time, so I dont overload it. The truck has had all of its recommended factory service up to date - and done by the dealer.
While driving back, it occured to me that in all three cases I purchased gasoline from a no-name brand place (loves or pride or something). The octane rating might have been 86, rather than the Chevron 87 I normally put it. So I ask my wife to read to from the factory manual about octane rating for the truck. The manual says to only use 87 octane, using lower octane may cause problems, especially at altitutde. Twin Falls is somewhat high 3700 feet, but we drove through passes much higher.
What could this be? Twin Falls has a magnetic anomaly? Bad gas? Too low of octane?