P0117

Diagnostic Chart:

Wiring Diagram:

The engine coolant temperature sensor 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. This sensor is used for fuel/ignition control, hot/low coolant light, coolant gage and fan.

DTC PARAMETERS
DTC P0117 will set if the ECT reads over 140°C (284°F) when the engine has been running over 10 seconds.

IMPORTANT: The ECT signal is continuously checked when ignition is On.

DIAGNOSTIC AIDS
Refer to Description and Operation in this section 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.

The PCM will turn the cooling fan On if a ECT diagnostic trouble code is set.
ECT may be compared to IAT temperature with Scan tool if engine has cooled overnight at ambient temperature. They should be within four degrees of each other with ignition On and engine Off.

CAUTION: TO AVOID THE DANGER OF BEING BURNED, DO NOT REMOVE 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 ECT should be within 15°F of each other.

Engine cooling fan also comes on if engine coolant temperature exceeds 106°C (223°F).

IMPORTANT: If a DTC P0117 is active, the temperature gage will read half.