Engine coolant thermostats used to be pretty simple devices. But as with everything else automotive, they now have electronic controls. Follow this Real Fix to see how a 2015 Opel/Vauxhall with a code P0597 for the thermostat heater control circuit was diagnosed and the component that caused the problem.
Vehicle
2015 Opel/Vauxhall Mokka 1.6 Petrol
Title
P0597, Replaced Engine Coolant Thermostat Housing
Complaint
The customer states the check engine light is on.
Cause
Connected a scan tool and found code P0597 – Thermostat Heater Control Circuit/Open. With the scan tool connected, monitored live data and found the engine coolant temperature was within the specified operating temperature. Used a multi-meter to backprobe the thermostat heater control electrical connector and found voltage and ground were present. Disconnected the connector from the thermostat heater control, inspected the connector, terminals and wiring harness and found no faults. Measured the resistance of the thermostat heater control and found no continuity. These test results verified the thermostat heater control was faulty. The thermostat heater control is integrated into the engine coolant thermostat housing and is replaced as an entire unit.
Correction
Replaced the engine coolant thermostat housing, cleared codes, performed a road test and verified the vehicle operated properly. The check engine light did not illuminate and no fault codes returned.