P0116
Medium SeverityEngine Coolant Temperature Sensor Range/Performance
Cooling System
P0116 — Instant Answer
Engine Coolant Temperature Sensor Range/Performance
Severity: MEDIUM SEVERITY
Meaning: 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.
Safe to drive? Usually yes with caution, but confirm root cause before long trips.
Estimated repair cost: $15 - $40
Most common causes:
- 1. Stuck-open thermostat (35-45% of cases)
- 2. Faulty ECT sensor (10-25% of cases)
- 3. Air pocket in cooling system (10-25% of cases)
- 4. Wrong thermostat temperature rating (5-10% of cases)
Symptoms
- ⚠️Slow warm-up
- ⚠️Temperature gauge stays low
- ⚠️Poor heater output
- ⚠️Increased fuel consumption
Common Causes
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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Related Codes
The ECT sensor circuit has a general malfunction. This sensor tells the ECM how warm the engine is for fuel, timing, and fan control.
The engine is not reaching normal operating temperature within the expected time. The thermostat is almost certainly stuck open.
ECT sensor voltage is too low, indicating an impossibly high temperature. Usually a shorted sensor.
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.
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Author & Review
Written by AllOEMManuals Editorial Team. Reviewed by ASE-certified technicians and updated with factory-reference checks for fitment-sensitive steps.
This guide was drafted with AI assistance and reviewed for accuracy by a human editor.
Last updated: 2026-05-07