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.

Real-world scan data

Seen in

768

scans in the past year

Found in

0.1%

of scans

0.2%

of scans that found faults

Appears alongside · share of P0597 scans

P0113in 14.7% of scans

P0037in 10.2% of scans

P2681in 9.9% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

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.

Read & clear P0597 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX