Hi everyone,
This is to help whoever can benefit from it.
First my background. 28 years as an ASE Master, L1, CA Smog Tech, B & L Inspector. Been doing this way too long!
This same issue started six months ago on my personal truck but it was very random to say the least. The problem would always disappear by the time I got to my destination until last week. Going by the symptoms, I knew this was a electrical/electronic problem and not a mechanical (thermostat) problem.
My diagnostics lead me to the BCM. Problem is that as soon as I touched the wire harness going to the BCM the fault disappeared and has not returned. I did however unplug and inspect for signs of poor connections and broken wires at the BCM. I have seen way to many times that wires will break inside the insulation due to excessive stress caused by engineers. The harness is very tight going to the BCM connectors. I hope this helps some you and I will add more if my ghost shows up again.