P0116
Medium SeverityEngine Coolant Temperature Sensor Range/Performance
Cooling System
What Does P0116 Mean?
The ECT sensor reading is not changing as expected during warm-up. Either the sensor is lazy or the thermostat is preventing normal warm-up.
Common Fix
Replace thermostat
Estimated Cost (DIY)
$15 - $40
Symptoms
- ⚠️Slow warm-up
- ⚠️Temperature gauge stays low
- ⚠️Poor heater output
- ⚠️Increased fuel consumption
Common Causes
Stuck-open thermostatlikely
Faulty ECT sensorpossible
Air pocket in cooling systempossible
Wrong thermostat temperature ratingunlikely
How to Diagnose P0116
- 1Monitor ECT temperature rise during warm-up
- 2Compare ECT to infrared thermometer reading
- 3Check thermostat operation
- 4Inspect for air in cooling system
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Frequently Asked Questions
- Is P0116 the thermostat or the sensor?
- Most commonly the thermostat is stuck open. If the engine truly does not reach operating temp, replace the thermostat first.
- How long should warm-up take?
- A healthy engine should reach 190-210°F within 5-10 minutes of driving. If it takes longer, the thermostat is likely stuck open.