P0116

CIRCUIT DESCRIPTION
The Engine Coolant Temperature (ECT) sensor contains a thermistor which changes resistance based on 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 (ECM) applies a voltage, about 5 volts, on the signal circuit to the sensor. The ECM monitors any changes in this voltage caused by 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.

CONDITIONS FOR RUNNING THE DTC
The engine is running.

CONDITIONS FOR SETTING THE DTC
The difference between the calculated engine coolant temperature and the actual engine coolant temperature is more than 12°C (22°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.
^ Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving any of the related connectors and the wiring harnesses. A change in the display may help in order to locate the fault.
^ Check for a stuck open thermostat. A stuck thermostat, during very cold ambient conditions, may cause the engine temperature to increase too slowly and may set this DTC.
^ 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 test will determine if a sensor is skewed. [1][2]Electrical Specifications
^ For intermittents, refer to Symptoms - Computers and Control Systems. Symptom Related Diagnostic Procedures

IMPORTANT: The low reference for the ECT sensor is shared with the Mass Air Flow (MAF) sensor, Camshaft Position (CMP) sensor, and the Throttle Position (TP) sensor. Do not use a test lamp to test the continuity of the low reference back through the ECM. Damage to the ECM will result.

^ 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 to determine if the sensor is skewed. [1][2]Electrical Specifications

TEST DESCRIPTION

Steps 1-11:

The numbers below refer to the step numbers on the diagnostic table.
3. This step tests for excessive resistance in the ECT circuit.
7. This step tests for a skewed sensor through the range of temperatures affecting this DTC.