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P0597 OBD-II Trouble Code: Thermostat Heater Control Circuit/Open

Check Engine Light

P0597 code definition

The P0597 trouble code signifies that a thermostat heater control circuit is open.

What the P0597 code means

If a PCM (Powertrain Control Module) stores this code, it’s because the engine’s thermostat is experiencing an issue with the control voltage. The control circuit is most likely either open or short. This thermostat is used to monitor the temperature of the engine and make adjustments to ensure it doesn’t overheat or suffer from other possible problems. Related codes are P0598 and P0599. The only difference between these three pertains to the make and model of the car. P0597 are used by German manufacturers like Mercedes, BMW, Volkswagen, Mini, Jaguar and Opel.

What causes the P0597 code?

The problem behind P0597 could be a number of things. However, more often than not, you’ll find that it was stored because of an issue with the electrical connector. Check to see if it’s corroded or loose. Otherwise, the issue could be:

  • The thermostat itself is faulty
  • There is a coolant leakage
  • The wiring harness between the thermostat has shorted or is open There is also a chance that the engine management computer – the Motronic – has failed. This is pretty rare, though, so it would be wise to exhaust other possibilities before checking it.

What are the symptoms of the P0597 code?

For the most part, code P0597 probably won’t cause any noticeable symptoms. Aside from the Check Engine light coming on, you may notice that your vehicle’s temperature gauge is reading abnormally high. Conversely, it could be showing a lower temperature than normal. It depends on what position the thermostat was in at the time of its failure. That being said, if the thermostat fails when the engine is cool, the vehicle runs a pretty good chance of overheating. Unfortunately, the driver probably won’t notice anything until it's already too late.

How does a mechanic diagnose the P0597 code?

Diagnosing the P0597 code problem will entail:

  • The first thing a mechanic will need to do is use an OBD-II scanner to confirm which codes have been stored.
  • Next, the technician should remove the electrical connector and inspect it for any obvious problems (e.g. corrosion).
  • The coolant level in the radiator will also need to be inspected as low amounts will make the thermostat overheat and trigger this code.
  • The electrical connector will also need to be removed so the mechanic can check the thermostat’s resistance values.

Common mistakes when diagnosing the P0597 code

A lot of mechanics go right to replacing the entire electronic thermostat. This may often solve the problem, but it’s not always necessary to do away with the whole thing either. Sometimes, the system circuitry is the real problem. Then, however, mechanics need to be careful to not just clean off or repair corroded wires, but also look for the source of this corrosion. An engine coolant leak is most likely the culprit. This will have to be repaired or the problem will repeat itself.

How serious is the P0597 code?

It’s not a serious problem insofar as it doesn’t represent a threat to the driver’s life. That being said, there’s a reason the thermostat is tasked with gauging engine heat and it’s because too much and the vehicle will quit performing. Worse yet, overheating can sometimes destroy the engine, which would lead to a costly replacement. For this reason, the problem shouldn’t be allowed to persist for long.

What repairs can fix the P0597 code?

The most common repairs for the P0597 code include:

  • Cleaning off or replacing damaged circuitry
  • Replacing the thermostat
  • Addressing a coolant leakage

Additional comments for consideration regarding the P0597 code

The P0597 code is the reason why drivers need to pay attention to their vehicles. If the hood of the vehicle feels hot to the touch after normal operation, but no Check Engine light came on, they should know something is wrong and they need to see a mechanic.

Need help with a P0597 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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