P0117

Circuit Description
The Engine Coolant Temperature (ECT) sensor contains a semiconductor device which changes the resistance based on the temperature (a thermistor). The ECT sensor is mounted in the left bank cylinder head near the front of the engine. The ECT sensor has a signal circuit and a ground circuit. The PCM applies a voltage (about 5.0 volts) on the signal circuit to the sensor. The PCM monitors the changes in this voltage caused by changes in the resistance of the sensor in order to determine the coolant temperature.

When the coolant is cold, the sensor (thermistor) resistance is high. The PCMs signal voltage is only pulled down a small amount through the sensor to a ground; therefore, the PCM senses a high signal voltage (low temperature). When the coolant is warm, the sensor resistance is low. The signal voltage is pulled down a greater amount; therefore the PCM senses a low signal voltage (high temperature). At normal operating temperature, the voltage should measure about 1.5-2.0 volts at the PCM. When the PCM senses a signal voltage lower than the normal operating range of the sensor, this DTC sets.

The PCM sends the Instrument Panel Cluster (IPC) engine coolant temperature information via the class 2 circuit. This information is used for controlling the coolant temperature gauge and for displaying a message when the coolant temperature is out of the normal operating range. The IPC displays a message when the engine coolant temperature is greater than 121°C (250°F).

Conditions for Running the DTC
The engine run time is greater than 10 seconds.
OR
The engine run time is less than 10 seconds when IAT is less than 50°C (122°F).

Conditions for Setting the DTC
^ The Engine Coolant Temperature is greater than 139°C (282°F).
^ All conditions met for 20 seconds.

Action Taken When the DTC Sets
^ The PCM illuminates the Malfunction Indicator Lamp on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure records.
^ The engine coolant temperature gauge defaults to a predetermined value.
^ The message center will display a message (this may only be displayed briefly).

Conditions for Clearing the MIL/DTC
^ The PCM turns the MIL OFF after three consecutive ignition cycles that the diagnostic runs and does not fail.
^ A last test failed (current DTC) clears when the diagnostic runs and does not fail.
^ A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
^ Use a scan tool in order to clear the MIL/DTC.

Diagnostic Aids

Important: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

^ The following may cause and intermittent:
- Mis-routed harness
- Rubbed through wire insulation
- Broken wire inside the insulation
^ If the engine has sat overnight, the engine coolant temperature and the intake air temperature values should display within a few degrees of each other. If the temperatures are not within 3°C (5°F), refer to Temperature vs Resistance.
^ If you determine that the DTC occurs intermittently, performing the P1114 diagnostic table may isolate the cause of the fault.
For an intermittent, refer to Symptoms. Symptom Related Diagnostic Procedures

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. This step determines if the malfunction is present.
3. Using the Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed. For any test that requires probing the PCM or component harness connectors, use the Connector Test Adapter Kit J 35616-A. Using this kit prevents any damage to the harness connector terminals.
4. An engine coolant temperature below -30°C (-22°F) indicates the PCM and the ECT sensor wiring are OK.
5. Disconnecting the PCM allows using the DMM J39200 in order to check continuity of the circuits. This aids in locating an open or a shorted circuit.
7. Inspect for proper terminal tension/connections at the PCM harness before replacing the PCM. Refer to Intermittents and Poor Connections Diagnosis.