Code Definition

P0118 — Engine Coolant Temperature Circuit High Input

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0118

P0118 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0118 is stored, the module has detected a signal or supply voltage higher than the expected operating range.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0118 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The P0118 code indicates a high input condition in the circuit of the Engine Coolant Temperature (ECT) sensor. This sensor monitors the temperature of the engine's coolant, providing essential data to the Engine Control Module (ECM) for managing engine functions such as fuel injection, ignition timing, and emission control. A high input signal from the ECT sensor may indicate an overestimation of coolant temperature, which can result in issues like improper engine warming up, increased emissions, and reduced fuel efficiency.

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