P0118

Diagnostic Chart:

Wiring Diagram:

The engine coolant temperature sensor (ECT) is a thermistor located in the lower coolant passage of the engine's cylinder head. When coolant temperature is cold the sensor has a high resistance, as temperature increases the resistance of the sensor decreases. The PCM provides a five volt signal to the coolant sensor, which is also connected to PCM ground. The PCM reads the voltage drop on the signal line to determine coolant temperature.

DTC PARAMETERS
DTC P0118 will set if the ECT reads below -35°C (-31°F) when the engine has been running longer than four minutes.

IMPORTANT: The ECT signal is continuously checked when the engine is running.

DIAGNOSTIC AIDS
Refer to Description and Operation for Temperature vs. Resistance Chart.

Start engine and observe ECT reading on Scan tool. Normal operation is for the ECT to rise smoothly to approximately 88°C (190°F), as thermostat opens then stabilizes.

Visually inspect ECT wires for damage. Wiggle wires while observing Scan tool ECT reading and watch for a sudden shift in temperature.

ECT may be compared to IAT temperature, with a Scan tool if engine has cooled overnight at ambient temperature. They should be within four degrees of each other with ignition On - engine Off.

CAUTION: TO AVOID THE DANGER OF BEING BURNED DO NOT REMOVE THE COOLANT SURGE TANK CAP WHILE THE ENGINE, RADIATOR AND TANK ARE HOT SCALDING FLUID AND STEAM CAN BE BLOWN OUT UNDER PRESSURE.

To verify coolant sensor integrity, install a thermometer in the coolant surge tank. With engine running and A/C Off, the temperature in the bottle and the Scan tool reading for engine coolant temperature should be within 15°F of each other.

IMPORTANT: If a DTC P0118 is active, the temperature gage will read half.