P0118
ECT Sensor Circuit High Input
medium
i Description
The Engine Coolant Temperature sensor is reporting an implausibly high voltage, suggesting an extremely low temperature to the ECU. This typically indicates an open circuit — the sensor is disconnected or has failed open.
? Common Causes
- Disconnected ECT sensor connector
- Open circuit in wiring
- Faulty ECT sensor (open)
- Corroded or spread connector pins
! Symptoms
- Check engine light
- Engine running rich
- Cooling fans not activating
- Temperature gauge reading very low or zero
- Black exhaust smoke
# Diagnostic Steps
- Check ECT sensor connector is plugged in
- Test wiring continuity
- Measure sensor resistance
- Replace if open-circuit
⚙ Typical Fix
Reconnect or replace the ECT sensor.
Parts Needed
ECT sensor
Estimated Cost
$30-$200
↔ Related Codes
Q Frequently Asked Questions
Use caution — the cooling fans may not turn on because the ECU thinks the engine is cold. Monitor engine temperature carefully to avoid overheating.
☞ Learn More
- What is OBD-II? — Complete guide to your car's diagnostic system
- How to Read DTC Codes — Step-by-step with a Bluetooth scanner
- OBD-II Scanner Buying Guide — Find the best scanner for your car