P0118

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

Circuit Description

The engine coolant temperature (ECT) sensor is installed to the thermostat housing. The ECT sensor is a variable resistor and it measures the temperature of the engine coolant. The sensor has a signal circuit and a low reference circuit. The ECM supplies 5 volts to the signal circuit and a ground for the low reference circuit. When the ECT sensor is cold the sensor resistance is high. When the engine coolant temperature increases the sensor resistance decreases. With high sensor resistance the ECM detects a high voltage on the signal circuit. With lower sensor resistance the ECM detects a lower voltage on the signal circuit. If the ECM detects an excessively high signal voltage this DTC will set.

Condition for Running the DTC

^ DTC P0117 is not set.
^ The battery voltage is between 10 to 16 volts.
^ The ignition switch is ON.
^ The engine is running.

Condition for Setting the DTC

^ The ECM detects that the ECT sensor signal voltage is more than 4.88 volts for 3 seconds.

Action Taken When the DTC Sets

^ The ECM illuminates the MIL when the diagnostic runs and fails. Refer to DTC Type Definitions for Action Taken When the DTC Sets - Type A.
^ The ECM uses an ECT substitution of default value.
^ The ECM limits fuel injection quantity.
^ The ECM inhibits EGR control.
^ The ECM inhibits DPF regeneration control.
^ The ECM inhibits cruise control.

Condition for Clearing the DTC

^ Refer to DTC Type Definitions for Condition for Clearing the MIL/DTC - Type A.

Diagnostic Aids

^ If an intermittent condition is suspected refer to Intermittent Conditions in this section.
^ Use the Temperature vs. Resistance table to test the ECT sensor at various temperature levels to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability concerns.

Circuit/System Testing DTC P0118