Engine coolant temperature sensor open circuit or internal failure. Loose, corroded, or damaged sensor wiring/connectors. Low coolant level or air pockets causing unstable readings.

Confirm coolant temperature readings with an OBD-II scanner. Inspect the sensor connector and wiring before replacing parts. Check coolant level only after the system has cooled.

P0118

Warning

Engine Coolant Temperature Circuit High Input

Severity

Warning

What does P0118 mean?

Fault code P0118 means the engine coolant temperature sensor circuit is reporting an unusually high voltage or implausible temperature signal. The engine control module may use a fallback temperature value, which can affect fan control, fuel strategy, and overheat protection.

Possible Causes

Engine coolant temperature sensor open circuit or internal failure
Loose, corroded, or damaged sensor wiring/connectors
Low coolant level or air pockets causing unstable readings
Thermostat, cooling fan, or coolant pump issue

Recommended Actions

1 Confirm coolant temperature readings with an OBD-II scanner
2 Inspect the sensor connector and wiring before replacing parts
3 Check coolant level only after the system has cooled
4 Avoid continued driving if overheating warnings appear
5 Schedule service if the code persists or returns after clearing

Related Powertrain fault codes

P0100 Mass or Volume Air Flow Circuit Malfunction P0102 Mass or Volume Air Flow Circuit Low Input P0103 Mass or Volume Air Flow Circuit High Input P0105 Manifold Absolute Pressure/Barometric Pressure Circuit P0107 Manifold Absolute Pressure/Barometric Pressure Circuit P0108 Manifold Absolute Pressure/Barometric Pressure Circuit P0110 IAT Circuit Malfunction P0117 Engine Coolant Temperature Circuit Low Input