OBD
P0597
Thermostat Heater Control Circuit/Open
What it means
P0597 means Thermostat Heater Control Circuit/Open.
Check these first
- A failed thermostat heater
- An open in the heater control circuit
- Corroded heater connector or wiring
- A blown heater fuse or relay
- A PCM driver fault
What to do next
- Check the heater fuse and relay
- Measure the thermostat heater resistance
- Inspect the heater connector and wiring
- Test the control circuit at the PCM
- Replace the thermostat heater if the element is open
- Clear the code and retest
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Updated
Generic SAE J2012 definition. Last updated 2026-10-10.