Engine Coolant Temperature Sensor 1 Circuit Range/Performance
What does P0116 mean?
The P0116 code means the vehicle's onboard diagnostic system has detected: Engine Coolant Temperature Sensor 1 Circuit Range/Performance. This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Heater may not produce hot air
- Temperature gauge reads low
- Extended warm-up time
- Poor cold-start fuel economy
Probable Causes (Ranked by Likelihood)
- Thermostat stuck open (engine never reaches operating temperature) Very High
- Partially failed ECT sensor giving slow or low readings High
- Air pocket in cooling system near sensor Moderate
- Incorrect thermostat temperature rating Moderate
Step-by-Step Diagnostic Procedure
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Monitor ECT reading during warm-up. It should reach operating temperature (typically 195-210F) within 5-7 minutes of driving.
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If temperature plateaus at 150-160F, the thermostat is likely stuck open. Replace it.
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Compare ECT reading to an infrared thermometer on the coolant hose near the sensor.
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Check for air in the cooling system by feeling for air bubbles at the sensor location.
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Replace ECT sensor if thermostat checks out normal.
Frequently Asked Questions
How do I know if it is the thermostat or the ECT sensor causing P0116?
Compare the scan tool ECT reading to an infrared thermometer on the coolant hose. If the scan tool reads much lower than the actual hose temperature, the sensor is at fault. If both read low after full warm-up, the thermostat is stuck open.