P0597
Thermostat Heater Control Circuit/Open
Cooling
Generic OBD-II
Medium
What it means
P0597 means the ECM detected an open in the control circuit for the map-controlled (electrically heated) thermostat. The heater lets the ECM open the thermostat earlier for better temperature control; with the circuit open the thermostat still works mechanically but runs at its default temperature, so the engine may sit slightly cooler than ideal and fuel economy can suffer a little.
Medium
Can I keep driving? Usually driveable — the engine may run slightly cooler than ideal, but keep an eye on the temperature gauge under heavy load.
Common symptoms
What you'll notice
- Check-engine light on
- Engine takes longer to warm up or runs below its ideal temperature
- Slightly reduced fuel economy
- Often no obvious change in how the car drives
Common causes
Most likely first
- Open circuit in the map-controlled (heated) thermostat's heater elementLikely
- Open or broken wiring in the heater control circuitCommon
- Corroded or loose connector at the thermostatCommon
- Less commonly, a faulty ECMLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data to see the conditions when it set.
- Inspect the thermostat heater connector and wiring for opens or corrosion.
- Measure the heater element's resistance and compare to spec.
- Replace the map-controlled thermostat if the heater is open.
- Repair any wiring faults, then clear the code and re-test.
FAQ
Quick answers
Is it safe to drive with P0597?+
Generally yes. The thermostat still opens and closes on temperature; the electric heater just can't fine-tune it. Watch the gauge under heavy load and repair it when convenient.
Can I just clear P0597?+
It will return until the heater circuit is repaired. Clearing alone doesn't restore the thermostat's electronic temperature control.
Related codes
Often seen with P0597
Read & clear P0597 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX