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P0117



DTC P0117

DTC DESCRIPTORS

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

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

DIAGNOSTIC FAULT INFORMATION






IMPORTANT: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

TYPICAL SCAN TOOL DATA

ECT Sensor Temperature:






CIRCUIT/SYSTEM 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 a ground for the ECT low reference circuit. When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance decreases. With high sensor resistance, the ECM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the ECT signal circuit.

CONDITIONS FOR RUNNING THE DTC

P0117
- The ignition is ON.
- DTC P0117 runs continuously within the enabling condition.

P0118
- The engine has been running for more than 8 minutes.
- DTC P0118 runs continuously within the enabling condition.

CONDITIONS FOR SETTING THE DTC

P0117
The ECM detects that the ECT Sensor parameter is more than 149°C (300°F) for more than 10 seconds. This is equal to less than 0.065 volt on the ECT signal circuit as measured by the ECM.

P0118
The ECT sensor temperature is less than -39°C (-38°F) for more than 10 seconds. This is equal to more than 4.8 volts on the ECT signal circuit, as measured by the ECM.

ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE DTC
- The control module turns OFF the 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
- If a short to a separate 5-volt source occurs, this DTC will set.
- A skewed sensor could result in poor driveability conditions. Refer to Temperature vs Resistance (ECT Sensor) Temperature vs Resistance (IAT Sensor) Temperature vs Resistance (IAT 2 Sensor) Temperature vs Resistance (Fuel Temperature).
- After starting the engine, the ECT should rise steadily, then stabilize when the thermostat opens.
- If the condition is suspected of being intermittent, refer to Testing for Intermittent Conditions and Poor Connections and Inducing Intermittent Fault Conditions.

CIRCUIT/SYSTEM VERIFICATION
1. Start the engine.
2. Observe the ECT sensor parameter with a scan tool.
3. The ECT sensor parameter should be within normal operating range.

CIRCUIT/SYSTEM TESTING

P0117
1. Disconnect the ECT sensor.
2. Turn ON the ignition with the engine OFF.
3. Observe the ECT sensor parameter with a scan tool.
- If the ECT sensor parameter is more than 149°C (300°F), test the ECT signal circuit for a short to ground or a faulty ECM.
- If the ECT sensor parameter is less than -39°C (-38°F), replace the ECT sensor.

P0118
1. Disconnect the ECT sensor.
2. Turn the ignition ON with the engine OFF.
3. Measure the voltage between the ECT signal circuit and a good ground with a DMM.
- If the voltage is more than 5 volts, test the ECT signal circuit for a short to voltage.
- If the voltage is less than 4.9 volts, test the ECT signal circuit for an open or a faulty ECM.
4. Measure the voltage between the ECT low reference circuit and the ECT signal circuit.
- If the voltage is more than 5 volts, test the ECT low reference circuit for a short to voltage or a faulty ECM.
- If the voltage is less than 4.9 volts, test the ECT low reference circuit for an open or a faulty ECM.
- If the voltage is between 4.9-5 volts, test the ECT low reference circuit and the ECT signal circuit for high resistance.
5. If the ECT sensor circuits test normal, replace the ECT sensor.

COMPONENT TESTING
Measure and record the resistance of the ECT sensor at various ambient temperatures and compare those measurements to the Temperature vs. Resistance Table.

REPAIR INSTRUCTIONS

IMPORTANT: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Engine Coolant Temperature (ECT) Sensor Replacement
- Control Module References for ECM replacement, setup, and programming
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