Appearance of the check engine light caused a scanner investigation showing just P0597 as the only diagnostic code. Since the cabin heater system seems to work fine and blows warm air, I'm going to presume that this issue is likely related to the main thermostat assembly. The wiring harness and connector attached to the thermostat assembly look to be in good condition without any signs of corrosion.
After removing the connector, I tried to see if I could measure any continuity/resistance on the two pins inside the connector on the thermostat assembly, but I don't seem to be getti
