Fault code P0597 is called “Thermostat Heater Control Circuit Open” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.
Technical description and explained code P0597
Error code P0597 is a generic code defined as an “open circuit in the thermostat heater control system”. It is set when the Powertrain Control Module (PCM) detects an open circuit in the motorized thermostat heater control circuit.
An electronically controlled thermostat uses wax pellets and a spring to control its operation just like a conventional thermostat. But the wax pellets are supplemented by a heater element controlled by the PCM to control its operation depending on driving conditions.
The PCM uses data from engine speed, throttle position, intake air temperature and engine coolant. It determines operating conditions and the appropriate thermostat setting. Which will bring the engine temperature into a range where emissions can be reduced without sacrificing fuel economy or engine efficiency.
For an electronically controlled thermostat to work properly, the electrical circuits must be in perfect working order.
When the PCM detects a breakage or loss of continuity in the thermostat control circuits, it realizes that it cannot control effectively. This will set the code P0597, and the warning light on the instrument panel will illuminate.
Symptoms of vehicle malfunctions
The main signal that an error P0597 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- Check engine control lamp on the control panel will light up (the code will be recorded in the memory as a fault).
- High temperature reading if the thermostat has failed in the closed position.
- Low temperature reading if the thermostat has failed in the open position.
Error P0597 is considered serious because the engine can overheat, which can cause damage to its components. If this code is detected, it is recommended that the fault is corrected as soon as possible.
Factors that can cause this error code
The error code P0597 can mean that one or more of the following problems have occurred:
- Faulty thermostat.
- Loose or corroded connector.
- Damaged, burned, or shorted wiring.
- Coolant leakage.
- Sometimes the cause is a faulty PCM module.
How to fix or reset OBD-2 code P0597
Some suggested steps for troubleshooting and fix the error code P0597:
- Read all stored data with an OBD-II scan tool.
- Check the coolant level in the radiator and expansion tank.
- Remove the electrical connector from the thermostat and check for corrosion and any damage.
- Measure the resistance at the connector.
- Inspect and test the wiring related to the thermostat.
Diagnose and repair of problems
The first step in the troubleshooting process for any malfunction is to review the Technical Service Bulletins (TSB). Check code P0597 for known problems with your particular vehicle.
Next, conduct a visual inspection of the wiring and connectors, and repair or replace any that are damaged, burned out, or damaged. Use a multimeter to check the voltage and ground circuits on the thermostat heater and PCM.
If no voltage is detected, check the system relays and associated fuses. Replace defective or blown fuses if necessary.
Test the thermostat heater control circuits and system components following the manufacturer’s instructions. If voltage and ground are not detected on the thermostat heater, check the corresponding circuit on the PCM connector.
If voltage is detected there, there is most likely an open circuit between the thermostat and the PCM. If no voltage is detected, the PCM may have failed or a programming error may have occurred.
It is a good idea to check the coolant level in the radiator. Low coolant level can cause the electronic thermostat to overheat and consequently set error P0597.
On which vehicles does this problem occur most frequently
Fault code P0597 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Audi (Q7)
- BMW (X5)
- Chevrolet (Aveo, Cruze, Orlando, Sonic, Spark)
- Citroen (C3, C4, C5)
- Daewoo (Matiz)
- Ford (Focus)
- Jaguar
- Mercedes-Benz (W204)
- Mini (Cooper)
- Nissan (Qashqai)
- Opel (Astra, Corsa, Mokka, Vectra, Zafira)
- Peugeot (207, 3008, 307, 308, 407, 408)
- Volkswagen (Passat)
Fault code P0597 can sometimes be found with other errors. The most common are the following: P0115, P0598, P0599, P2096, P2178, P2270.
