P0597 Code Explained: Common Symptoms and Solutions

P0597 Code Explained: Common Symptoms and Solutions

The P0597 code stands for “Thermostat Heater Control Circuit/Open.” This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an issue with the thermostat heater control circuit, specifically when the control voltage is zero or outside the expected range. This code is commonly found in vehicles with electronically controlled thermostats, which are designed to improve engine efficiency and emissions by precisely managing the engine’s temperature.

Top 20 Vehicles Commonly Affected by the P0597 Code

  • BMW 3 Series
  • BMW 5 Series
  • Audi A4
  • Audi Q5
  • Mercedes-Benz C-Class
  • Mercedes-Benz E-Class
  • Mini Cooper
  • Volkswagen Golf
  • Volkswagen Passat
  • Opel Astra
  • Chevrolet Cruze
  • Chevrolet Malibu
  • Chevrolet Equinox
  • GMC Terrain
  • Cadillac CTS
  • Cadillac Escalade
  • Buick Encore
  • Buick Regal
  • Volvo S60
  • Jaguar XF

Implications on Vehicle Performance and Emissions

When the P0597 code is triggered, it indicates that the thermostat is not functioning correctly, which can lead to several issues:

  • Overheating or Underheating: The engine may run too hot or too cold, leading to inefficient combustion and potential engine damage.
  • Increased Emissions: An improperly regulated engine temperature can result in higher emissions, as the engine may not operate within its optimal temperature range.
  • Reduced Fuel Efficiency: The engine’s fuel efficiency can decrease if it is not running at the correct temperature.
  • Cooling Fan Issues: The radiator’s cooling fans may run continuously, even when not needed, leading to unnecessary wear and tear.

Diagnosing and Fixing the P0597 Code

Key Symptoms

  • Check engine light illumination
  • Abnormal engine temperature readings (either too high or too low)
  • Continuous operation of the radiator cooling fans
  • Potential coolant leaks

Diagnostic Steps

  1. Visual Inspection:
    • Check the thermostat housing and connectors for any signs of damage or corrosion.
    • Inspect the wiring for any shorts, opens, or loose connections.
  2. Check Coolant Levels:
    • Ensure the coolant level is adequate. Low coolant levels can cause the thermostat to malfunction.
  3. Test the Thermostat:
    • Use a multimeter to check the electrical resistance of the thermostat. Refer to the vehicle’s service manual for the correct resistance values.
  4. Scan for Additional Codes:
    • Use an OBD-II scanner to check for any other related trouble codes that might provide more context.

Fixing the Issue

  • Clean and Secure Connections:
    • Remove any corrosion from the thermostat connectors using a baking soda solution and ensure all connections are tight and secure.
  • Replace the Thermostat:
    • If the thermostat is faulty, replace it with a new one. Ensure the new thermostat is compatible with your vehicle’s make and model.
  • Check and Repair Wiring:
    • Repair any damaged wiring and ensure there are no shorts or open circuits.
  • Inspect the PCM:
    • In rare cases, the Powertrain Control Module (PCM) may be faulty. If all other components are functioning correctly, consider having the PCM inspected and replaced if necessary.


1. Is it safe to drive with the P0597 code?

  • While the vehicle may still be drivable, it is not recommended to continue driving with this code. The engine is at risk of overheating or running inefficiently, which can lead to more severe damage and higher repair costs.

2. What are the potential repair costs for the P0597 code?

  • Repair costs can vary depending on the vehicle and the extent of the issue. Replacing a thermostat typically costs between $150 and $300, including labor. If the PCM needs replacement, costs can be significantly higher, ranging from $500 to $1,200.

3. How can I prevent the P0597 code from occurring?

  • Regular maintenance is key. Ensure your vehicle’s cooling system is in good condition, check coolant levels regularly, and address any leaks or wiring issues promptly.


Addressing the P0597 code promptly is crucial for maintaining your vehicle’s efficiency and compliance with emission standards. Ignoring this issue can lead to more severe engine damage and higher repair costs. If you’re not confident in diagnosing and fixing the problem yourself, seek help from a professional mechanic to ensure the issue is resolved correctly. Regular maintenance and timely repairs will keep your vehicle running smoothly and efficiently.

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