P0118

DTC P0118

Circuit Description

The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The engine control module (ECM) supplies 5 volts to the ECT signal circuit and supplies a ground to the low reference circuit. If the ECM detects an excessively high ECT signal voltage, which is a low temperature indication, this DTC sets.

The following table illustrates the difference between temperature, resistance, and voltage:






DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage

Conditions for Running the DTC

* The engine is running for more than 120 seconds.

* This DTC runs continuously once the above condition is met.

Conditions for Setting the DTC

The ECM detects that the ECT sensor is less than -39°C (-38°F) for more than 6 seconds.

Action Taken When the DTC Sets

* The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

* The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

Conditions for Clearing the MIL/DTC

* The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

* A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

* A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

* Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

* Test the ECT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor can result in a driveability condition.

* If the engine has sat overnight, the ECT sensor and the intake air temperature (IAT) sensor values should display within 3°C (5°F). Refer to Temperature Versus Resistance Temperature Versus Resistance.

* For an intermittent condition, refer to Intermittent Conditions Intermittent Conditions.