P0597: Thermostat heater circuit open
Thermostat heater control circuit/open
Severity: Inspect soon
The computer cannot control the electrically heated thermostat. Genesis says its bulletin case has no drivability issues, but Kelley Blue Book warns that losing temperature control raises overheating risk.
It gets more serious if:
- Stop: Stop if the temperature gauge climbs, a hot-engine warning shows, or steam appears.
P0597 in short
P0597 means the computer sees an open circuit in the heater of the electronically controlled thermostat. A failed thermostat or a wiring or connector fault is the usual cause. Some Genesis G80 and G90 cars have no drivability problems with it, but watch the temperature gauge and get it checked soon.
Some engines use a thermostat with a built-in heater that the computer switches on to open the thermostat early and run the engine cooler when needed. P0597 sets when the computer sees the heater circuit as open or its feedback as out of range.
The thermostat itself is the usual failure. Corroded or loose wiring to it is the next most common cause, and the engine computer is a rare one.
Genesis has a bulletin for certain G80 and G90 cars that replaces the electric thermostat for P0597 and says no drivability issues go with the condition. Kelley Blue Book is more cautious and warns about overheating if temperature control is lost.
Most likely causes
Cause 1: Failed electronically heated thermostat
Supported by vehicle data- Why it ranks here
- KBB lists the thermostat first, and Genesis has a bulletin that replaces the electric thermostat for P0597 on G80 and G90 cars. Only the NHTSA summary was read.
- What would change this
- Rises if the heater element reads open when tested. Falls if the heater resistance is normal.
Cause 2: Corroded or loose thermostat connector or wiring
Common general cause- Why it ranks here
- KBB lists corroded or improperly connected wiring.
- What would change this
- Rises if the connector is corroded or loose. Falls if the harness tests normal to the computer.
Cause 3: Engine computer fault
Possible — needs testing- Why it ranks here
- KBB says a defective computer is rare.
- What would change this
- Rises only after the thermostat and wiring pass testing.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Watch the temperature gauge or coolant temperature live data as the engine warms and check for fans running constantly.
IfTemperature climbs high or the gauge is erratic
It meansStop driving and have it towed or inspected.
IfTemperature looks normal
It meansInspect the thermostat connector next.
Step 2: Look at the thermostat connector and wiring for corrosion, damage or a loose plug.
Warning:Let the engine cool fully before touching anything near the cooling system; hot coolant can scald.
IfThe connector is corroded or damaged
It meansRepair it, clear the code and recheck.
IfThe connector looks fine
It meansHave the heater element and thermostat tested.
Step 3: Have a shop measure the thermostat heater resistance and the circuit back to the computer.
Warning:The thermostat sits in the hot coolant path. Let a shop do the testing.
IfThe heater is open or out of range
It meansThe thermostat needs replacing.
IfThe heater is fine and the circuit has continuity
It meansThe computer is a remote possibility.
Symptoms
- Check engine light on
- Temperature gauge reading too high or too low
- Radiator fans running all the time
- Hot-engine warning Gets more serious: stop and have it checked.
How to fix
Step 1: With the engine fully cool, check the coolant level in the reservoir and top up with the coolant your manual specifies.
Warning:Never open the radiator or reservoir cap on a hot engine.
Step 2: Ask a dealer whether your VIN has a bulletin for P0597.
Parts and cost context
- Thermostat:On engines with a heated thermostat the whole electric thermostat is usually replaced. Labor varies; get a quote.
Labor varies by vehicle and shop; get a quote before you approve a repair.
Compare used part prices on PartPriceGuideOn your vehicle
VolvoYour car
2015 · XC60
Supported by vehicle dataVolvo technical journal TJ30268 covers thermostat DTCs, including P0597, on 2015 Drive-E engines. Whether the bulletin is still current is not verified.
TJ30268Status unverified
Drive-E thermostat DTCs stored in the ECM
2015xc60 · NHTSA 10088748
Technical journal for thermostat DTCs on 2015 Drive-E engines. The summary does not give the repair.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
Related codes
No curated relationships for P0597 yet.
P0597 questions
Is it safe to drive with P0597?
Genesis says its bulletin cases have no drivability issues, but loss of thermostat control can lead to overheating. Watch the gauge and stop if it rises.
Does P0597 mean the thermostat is stuck?
Not exactly. It means the heater circuit inside the electronic thermostat reads open or out of range, which usually points at the thermostat or its wiring.
Sources and review
- P0597 code: thermostat heater control circuit/open
- 20-EM-003HG: P0597 thermostat heater control circuit/open
- TJ30268: Drive-E thermostat DTCs stored in the ECM
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error