Engine Coolant Temperature

The engine computer measures how hot the coolant is. If it’s too high or too low, the computer raises a flag to let you know something's wrong, which could affect performance.

The engine control module (ECM) expects coolant temperatures to be between 180°F and 220°F. If it reads lower than 140°F or higher than 240°F after the engine warms up, it triggers this fault code.

Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.

1. 11. Check the coolant level in the reservoir; it should be at the proper level. If low, top off and check for leaks. Decision: Is coolant level okay? If no, top off and retest. If yes, proceed to step 2.
2. 22. Inspect the wiring and connector at the coolant temperature sensor for damage, corrosion, or loose connections. Decision: Is the wiring intact? If no, repair or replace as needed. If yes, proceed to step 3.
3. 33. Use a scan tool to monitor the actual coolant temperature and compare it with the expected range. Start the engine and allow it to reach operating temperature. Decision: Is the sensor reading between 180°F and 220°F? If no, replace the coolant temperature sensor. If yes, proceed to step 4.
4. 44. Check the engine thermostat operation. It should open at around 195°F. Decision: Is the thermostat operating correctly? If no, replace the thermostat. If yes, proceed to step 5.
5. 55. Clear the fault code and take the vehicle for a road test. Monitor for reoccurrence. Decision: Does the code return? If yes, inspect the ECM for issues.

• Faulty coolant temperature sensor
• Wiring issues or poor connections
• Low coolant level or leaking coolant
• Thermostat stuck open or closed

$100-$300