P0118
High 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
Related Symptoms
Common Causes
How to Diagnose P0118
- 1Check ECT connector is plugged in
- 2Measure sensor resistance
- 3Check wiring continuity
- 4Replace sensor if open
OEM Diagnostic Flowchart
Scroll to load technician if/then branches.
Read live data and freeze frame for P0118 to pinpoint the cause before buying parts.
Related Resources
Repair guides, symptom pages, and wiring diagrams related to P0118.
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.
ECT sensor voltage is too low, indicating an impossibly high temperature. Usually a shorted sensor.
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.
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.