P0118
DTC P0118CIRCUIT 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 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 60 seconds.
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 vehicle has set overnight, the ECT sensor and the intake air temperature (IAT) sensor values should display within 3°C (5°F). Refer to Temperature vs Resistance.
- For an intermittent condition, refer to Intermittent Conditions. Intermittent Conditions
TEST
Steps 1-4:
Steps 5-8:
Steps 9-12:
