P0597
Thermostat Heater Control Circuit Open
The map-controlled thermostat - electrically heated to lower its opening temperature on demand for emissions or torque mapping - has an open control circuit. The ECU loses the ability to override coolant flow timing.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Open in heater element or harnessCommon
- Pin pushed back out of connector bodyLess likely
- Cracked solder joint inside the module or sensorLess likely
Parts involved
- MAP Thermostat Heater
P0597 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.