This is a weird one I have to admit.
Going to drop the car off to my mechanic tomorrow. He's going to drive it home so he can get it out on the road.
I'll suggest he disconnect the controller after he sees what it's doing.
I'll let you know what comes of it so you can file it away for future reference.
Got another one if you're interested.
Temperature spikes to the red line after it warms up and then drops back to about 90C. However, it fluctuates with stop and go driving. Have replaced the thermostat and sensor on the thermostat housing. Problem still exists.
Have seen this discussed in another forum here, but nobody appeared to have a satisfactory answer to what is causing it. My mechanic suggested a bad ground might be the source of the problem. What do you think?