P0118

Diagnostic Chart:

Schematic:

The Engine Coolant Temperature (ECT) sensor is a thermistor that varies resistance according to changes in engine coolant temperature. The PCM supplies a five volt reference through a pull-up resistor to the sensor, which is connected to ground. When the sensor is cold it has high resistance (high signal voltage at PCM). As the sensor temperature increases, its resistance decreases (low signal voltage at PCM). The PCM uses the signal voltage to determine engine coolant temperature. DTC P0118 sets when the ECT sensor signal voltage at the PCM is above the calibrated voltage value (below the calibrated temperature value).

DTC PARAMETERS
DTC P0118 will set if ECT temperature is below -35°C (-31°F) when engine has been running longer than 4.2 minutes.

DTC P0118 diagnostic runs continuously once the above conditions have been met.

DTC P0118 is a type A DTC.

DIAGNOSTIC AIDS
To locate an intermittent problem, use Scan tool to monitor ECT temperature with ignition On, engine Off. Wiggling wires while watching for a change in ECT temperature may locate the area where an open or short to voltage in the wiring could lie.

An intermittent open in ECT sensor can set this DTC. Run engine after it has cooled down and monitor ECT The temperature should rise smoothly to 88°C (190°F) as the thermostat opens and stabilizes the temperature of the engine coolant.

The PCM will turn the cooling fan On if an ECT DTC is active.

The Coolant Temperature telltale will read COLD if DTC P0118 is active.

Refer to ECT Sensor General Description for a Temperature vs. Resistance chart.

NOTE: A short to B+ on signal circuit 410 may damage the ECT sensor. Check for correct resistance vs. temperature after repair has been made.