P0118

Wiring Diagram:

ECT Sensor Circuit High Voltage/Low Temp:

P0118 - ECT SENSOR CIRCUIT HIGH VOLTAGE/LOW TEMP
The engine coolant temperature (ECT) sensor is a thermistor that varies resistance according to changes in engine coolant temperature. The ECM 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 ECM). As the sensor temperature increases. its resistance decreases (lower signal voltage at ECM). The ECM uses the signal voltage to determine engine coolant temperature. DTC P0118 sets when the ECT sensor signal voltage at the ECM is below the calibrated voltage value (over the calibrated temperature value).

DTC PARAMETERS
DTC P0118 will set if ECT sensor temperature is below -39°C (-38°F) when.
^ Condition exists for longer than 0.5 seconds
^ Engine speed is greater than 20 rpm

DTC P0118 diagnostic runs continuously with engine cranking/running

P0118 is a type B DTC

DIAGNOSTIC AIDS
To locate an intermittent problem, use Scan tool to monitor ECT sensor temperature with ignition On, engine Off. Wiggling wires while watching for a change in ECT sensor temperature may locate the area where a short to ground may exist.

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

The Coolant Temperature gauge will display COLD if DTC P0118 is active.

The ECM will command the cooling fans On if DTC P0118 is active.

The CMP/ECT/IAT/EGR/MAF/MAP/TP1/TP2 sensors share the same sensor return circuit 652.

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

IMPORTANT: A direct short to voltage on circuit 652 may cause internal damage to the ECM ground trace. or open the sensor element in the ECT, IAT and/or MAP sensors.