P0117

DTC P0117: Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage

Wiring Diagram:

Circuit Description
The Engine Coolant Temperature (ECT) sensor uses a thermistor to control the signal voltage to the Engine Control Module (ECM). The ECM supplies a voltage on the signal circuit to the sensor. When the engine coolant is cold, the resistance is high; therefore the ECT signal voltage will be high. As the engine warms, the sensor resistance becomes less, and the voltage drops. At normal engine operating temperature, the voltage will be between 1.5 and 2.0 V at the ECT signal terminal.

The ECT sensor is used to the following items:
- Fuel delivery.
- Lock Up Clutch (LUC).
- Ignition.
- Evaporative (EVAP) Emission Canister Purge Valve.
- Electric cooling fan.

Conditions for Setting the DTC
- Ignition ON.
- ECT voltage is less than 0.3419 V for more than 1 second.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn OFF at the end of a consecutive validation cycle in which the diagnostic runs without a fault.
- A history DTC will clear after 40 warm up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.

Diagnostic Aids
After the engine has started, the ECT should rise steadily to about 90 degrees C (194 degrees F) then stabilize when the thermostat opens.
Use the temperature vs. Resistance values table to evaluate the possibility of a skewed sensor. Refer to Engine Controls Description.

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DTC Troubleshooting