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 supplies a ground to the low reference circuit. The ECM monitors the mutual performance of the ECT and the intake air temperature (IAT) signals. The ECM monitors the warm up and cool down behavior of the sensors, after a vehicle driven at operating temperature is shut down. If the ECM detects that the ECT is not with in a predetermined range of IAT after a long soak, or the ECT and IAT are not within a range of each other, as compared to a previous cold start, this DTC sets.

The following table illustrates the difference between temperature, resistance, and voltage:

Condition 1

Condition 2

DTC P0116 is a Type A/B DTC.

DTC P0116 is a Type A/B DTC.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, observe the DTC information with a scan tool. DTC P0101, P0117, P0118, or P0119 should not be set.

⇒	If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for diagnosis of the applicable DTC.

2. Inspect the engine coolant level. Verify that the cooling system is operating correctly.

⇒	If you suspect a condition with engine cooling system, refer to Symptoms - Engine Cooling.

3. Inspect the thermostatically-controlled coolant heater, if equipped, for damage or modifications. Test for proper operation of the coolant heater. Refer to Coolant Heater Inoperative.
4. Ignition ON, verify the P0116 Freeze Frame Start Up ECT and the Start Up IAT parameters are within 14°C (25°F).
5. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

1. Ignition OFF, disconnect the ECT sensor.
2. Remove the fuse that supplies B+ to circuit terminal X2-56 of the ECM.

Caution: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw.

Note: The control module or the sensor may be damaged if the circuit is shorted to battery positive voltage.

3. Test for less than 5 Ω between the low reference circuit terminal 2 and ground.

⇒	If greater than the specified value, test the low reference circuit for an open/high resistance, or for a short to voltage. If the circuit tests normal, replace the ECM.

4. Install the fuse that supplies B+ to circuit terminal X2-56 of the ECM.
5. Ignition ON, verify the scan tool ECT sensor parameter is at -40°C (-40°F).

⇒	If greater than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.

Note: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage and the sensor may be damaged.

6. Ignition ON, install a 3 A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2. Verify the scan tool ECT sensor parameter is warmer than 142°C (288°F).

⇒	If colder than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

7. If all circuits test normal, test or replace the ECT sensor.

1. Ignition OFF, disconnect the harness connector of the ECT sensor.

Note: A thermometer can be used to test the sensor off the vehicle.

2. Test the ECT sensor by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the Temperature Versus Resistance - Engine Coolant Temperature Sensor table and verify that the resistance is within 5 % of the specification.

⇒	If not within the specified range, replace the ECT sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.