P0118
Medium SeverityEngine Coolant Temperature Sensor Circuit High
Cooling System
What Does P0118 Mean?
ECT sensor voltage is above maximum, reading as extremely cold. Usually an open sensor circuit.
Common Fix
Replace ECT sensor or repair connection
Estimated Cost (DIY)
$10 - $25
Symptoms
- ⚠️Fans never turning on
- ⚠️Rich running when cold
- ⚠️Poor cold-start idle
- ⚠️Check engine light
Common Causes
Open circuit ECT sensorlikely
Disconnected sensor connectorlikely
Broken wirepossible
How to Diagnose P0118
- 1Check ECT connector is plugged in
- 2Measure sensor resistance
- 3Check wiring continuity
- 4Replace sensor if open
Need to read or clear this code?
Shop OBD2 Scanners on Amazon →Frequently Asked Questions
- Will P0118 prevent fans from running?
- Yes — the ECM thinks the engine is cold, so it will not activate the cooling fans. This can lead to actual overheating. Fix immediately.
- Is P0118 dangerous?
- Potentially yes — if the fans do not run, the engine can overheat in traffic. Fix right away.