Engine is NOT actually overheating??? Not a simple thermostat stuck closed???
If that isn't the case, I'd strongly suspect a bad sensor or grounded sensor wire.
***Sensor is a linear resistance curve 4300-180 ohms, decreasing with temperature rise.
"overheat warning" usually occurs at around the 80-100 ohm value. ***
Sensor testing
- Disconnect sensor wire.
- Sensor pin to ground (60*F +/- 4300 ohms, 212*F +/- 180 ohms)
**** At running temp, if sensor reads less then 80 ohms, it has most likely failed****
- wire to ground should have +/- 12volts to ground while disconnected from sensor, key on.
-possibly got water into the sensor itself, Unlikely, but have had it happen to myself on a couple of occasions.
If you were aggressively washing inside the cab, you may have gotten the control panel wet.
I do wash my interiors carefully on occasion, but have never had a failure of the control panel.
***We are all extremely careful NOT to blast our interior electronics with washguns I would hope.