Engine Coolant Temperature Sensor Performance (GM)
What does P1116 mean?
The P1116 code means the vehicle's onboard diagnostic system has detected: Engine Coolant Temperature Sensor Performance (GM). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Engine temperature gauge reads incorrectly
- Poor fuel economy
- Cooling fans cycling erratically
- Delayed or no warm-up indication
Probable Causes (Ranked by Likelihood)
- Failing engine coolant temperature (ECT) sensor Very High
- Stuck-open thermostat preventing proper warm-up High
- Low coolant level exposing ECT sensor Moderate
- Air pocket in cooling system near ECT sensor Moderate
- Corroded ECT sensor or connector Low
Step-by-Step Diagnostic Procedure
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Check coolant level and inspect for leaks
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Monitor ECT sensor readings during warm-up -- temperature should rise steadily
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Compare ECT sensor reading to actual coolant temperature with an infrared thermometer
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Test the thermostat by checking upper radiator hose temperature during warm-up
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Replace the ECT sensor if readings do not track with actual temperature
Frequently Asked Questions
What does P1116 mean?
P1116 on GM vehicles indicates the engine coolant temperature sensor is not performing within expected parameters. The PCM expects coolant temperature to rise at a certain rate after a cold start, and this code sets when that does not happen.
Could a stuck thermostat cause P1116?
Yes. A thermostat stuck open will prevent the engine from reaching normal operating temperature, which can trigger P1116. Check the thermostat before replacing the ECT sensor.
How do I bleed air from the cooling system?
On most GM vehicles, fill the cooling system with the radiator cap off, start the engine, and let it idle until the thermostat opens. Top off the coolant as air purges. Some models have a bleed valve on the thermostat housing.