What are the common causes of P0118?

Open circuit in the ECT sensor signal wire. Faulty engine coolant temperature sensor. Poor connector connection or corroded terminals. Low coolant level causing false readings. PCM fault.

Check engine coolant level and top off if low. Inspect ECT sensor wiring and connector for opens or corrosion. Compare ECT reading on an OBD-II scanner with engine temperature. Verify sensor signal and ground circuits at the connector. Replace the ECT sensor if the circuit tests point to it.

P0118

Engine Coolant Temperature Circuit High Input

System: Fuel and air metering (P code)
Lamp: Check Engine Light
Category: Powertrain - Fuel/Air Metering

What it means

P0118 means Engine Coolant Temperature Circuit High Input.

Check these first

Open circuit in the ECT sensor signal wire
Faulty engine coolant temperature sensor
Poor connector connection or corroded terminals
Low coolant level causing false readings
PCM fault

What to do next

Check engine coolant level and top off if low
Inspect ECT sensor wiring and connector for opens or corrosion
Compare ECT reading on an OBD-II scanner with engine temperature
Verify sensor signal and ground circuits at the connector
Replace the ECT sensor if the circuit tests point to it

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Updated

Generic SAE J2012 definition. Last updated 2026-08-30.