P0115

CIRCUIT DESCRIPTION
The Engine Coolant Temperature (ECT) sensor contains a thermistor which changes resistance based on the temperature. The ECT sensor is located in the coolant crossover pipe at the center rear of the engine. The ECT sensor has a signal circuit and a ground circuit. The engine control module Engine Control Module (ECM) applies a voltage, about 5 volts, on the signal circuit to the sensor. The ECM monitors the changes in this voltage that are caused by the changes in the resistance of the sensor in order to determine the engine coolant temperature.

When the engine coolant is cold, the sensor resistance is high, and the ECM will sense a high signal voltage or low temperature. When the engine coolant is warm, the sensor resistance is low. This causes the ECM to sense a low signal voltage or high temperature.

When the ECM senses a signal voltage outside of the normal operating range of the sensor, this Diagnostic Trouble Code (DTC) will set.

CONDITIONS FOR RUNNING THE DTC
The ignition is ON.

CONDITIONS FOR SETTING THE DTC
The ECT signal voltage indicates an ECT that is more than 139°C (282°F).

OR

The ECT signal voltage indicates an ECT that is at -40°C (-40°F).

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 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.
^ Use a scan tool in order to clear the MIL and the DTC.

DIAGNOSTIC AIDS
^ Use the J 35616-A Connector Test Adapter kit for any test that requires probing the ECM harness connector or a component harness connector. Using this kit prevents damage to the harness or component terminals. Refer to Using Connector Test Adapters in Diagrams.
^ Check for poor connections at the ECM or at the component.
^ Use the Temperature vs Resistance Engine Coolant Temperature (ECT) Sensor table may be used in order to test the ECT sensor at various temperature levels. This will aid in determining if the sensor is skewed. A skewed sensor may cause a driveability concern. [1][2]Electrical Specifications
^ For intermittents, refer to Symptoms - Computers and Control Systems, Preliminary Checks. Symptom Related Diagnostic Procedures
^ If other DTCs are set that share the same ground circuit, test the point where the circuits splice and where the circuit connects to the ECM for opens or high resistance.
^ If the engine has been allowed to sit overnight, the engine coolant temperature and the Intake Air Temperature (IAT) 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 - Engine Coolant Temperature (ECT) Sensor.

TEST DESCRIPTION

Steps 1-10:

Steps 11-21:

Steps 22-24:

The numbers below refer to the step numbers on the diagnostic table.
2. Turn ON the engine and monitor the ECT on the scan tool. The ECT sensor temperature should rise steadily with the temperature of the engine.
5. Using the Freeze Frame data may aid in locating an intermittent condition. If the DTC cannot be duplicated, review the information in the Freeze Frame. Try to operate the vehicle within the same Freeze Frame conditions, the RPM, the MAF, the vehicle speed, the temperature, that were noted. This process may help to recreate the malfunction.
6. This step tests for proper operation of the circuit in the high voltage range.
8. This step tests for a short to voltage on the ECT sensor signal circuit.
11. This step tests the integrity of the reference ground circuit through the ECM to battery ground. Make sure the ECM has shut down prior to measuring the reference ground circuit resistance. This can be verified by the loss of communication on the scan tool. Do not use a test lamp to test the continuity of the reference ground circuit Damage to the ECM will result.
22. Perform the idle learn procedure when replacing the ECM or throttle body.