| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. | 
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. | 
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. | 
Circuit  | Short to Ground  | Open/High Resistance  | Short to Voltage  | Signal Performance  | 
|---|---|---|---|---|
ECT Sensor Signal  | P0117  | P0118  | P0118¹  | P0116  | 
Low Reference  | --  | P0118  | P0118¹  | P0116  | 
¹ ECM or sensor damage may occur if the circuit is shorted to B+.  | ||||
Circuit  | Short to Ground  | Open  | Short to Voltage  | 
|---|---|---|---|
Operating Conditions: Engine operating in Closed Loop. Parameter Normal Range: Varies with ambient temperature.  | |||
ECT Sensor Signal  | 129°C (264°F), 0.0 Volts  | -40°C (-40°F), 5.0 Volts  | -40°C (-40°F), 5.0 Volts¹  | 
Low Reference  | --  | -40°C (-40°F), 5.0 Volts  | --  | 
¹ ECM or sensor damage may occur if the circuit is shorted to B+.  | |||
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 following table illustrates the difference between temperature, resistance, and voltage:
ECT  | ECT Resistance  | ECT Signal Voltage  | 
|---|---|---|
Cold  | High  | High  | 
Warm  | Low  | Low  | 
| • | DTCs P0117, P0118, P0562, P0563, and P2610 are not set. | 
| • | The engine is operating. | 
| • | The ignition has been off for more than 6 hours before vehicle is started. | 
| • | The DTC runs when the above conditions are met. | 
The ECM does not detect an engine coolant temperature (ECT) sensor change of more than 3°C (5°F).
DTC P0116 is a Type B DTC.
DTC P0116 is a Type B DTC.
| • | After starting the engine, the ECT sensor temperature should rise steadily, then stabilize after the thermostat opens. | 
| • | Test the ECT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor can result in a driveability condition. Refer to Temperature Versus Resistance . | 
| • | Inspect for the correct operation of the engine cooling system and verify the correct coolant level. | 
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
| ⇒ | If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle . | 
| ⇒ | If greater than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM. | 
| ⇒ | If greater than the specified value, test the low reference circuit for a short to voltage. If the circuit/connections test normal, replace the ECM. | 
| ⇒ | If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit/connections test normal, replace the ECM. | 
Important: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage and the sensor may be damaged.
| ⇒ | If less than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit test normal, replace the ECM. | 
Important: A thermometer can be used to the used to test the sensor off the vehicle.
| ⇒ | If the resistance Vs. temperature is not within 5 percent, replace the ECT sensor. | 
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for engine control module replacement, setup, and programming |