Engine Coolant Temperature Sensor Range/Performance
The coolant temperature sensor reading does not change plausibly during warm-up, or its value disagrees with the intake air temperature when the engine has been off long enough that they should match. Often caused by a sensor that reports near a fixed value despite engine warm-up.
Affected components
- Coolant temperature sensor
- Thermostat
Common causes
- High likelihood: Sensor drifting outside specification
- Medium likelihood: Thermostat stuck open (engine never reaches operating temperature)
- Low likelihood: Sensor element aged beyond calibration window
Possible symptoms
- Check engine light on
- Cooling fan runs constantly or not at all
- Cabin heater weak or excessively hot
- Possible long warm-up time or hard cold start
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.