• | 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 | P0118* | P0116 |
Low Reference | -- | P0118 | P0118* | P0116 |
* 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 | 150°C (302°F) | -40°C (-40°F) | -40°C (-40°F)* |
Low Reference | -- | -40°C (-40°F) | -40°C (-40°F)* |
* ECM or sensor damage may occur if the circuit is shorted to B+. |
This diagnostic determines if the ECT sensor 1 is biased warmer than normal. The ECM will record the amount of time the engine is OFF. If the required engine OFF time is met at start-up, the ECM compares the temperature difference between the ECT and the IAT sensor. If the ECM detects that the temperature difference is greater than a calibrated amount, the ECM sets the DTC.
The engine coolant temperature (ECT) sensor 1 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 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 P0112, P0113, P0117, P0118, P0502, P2610 are not set. |
• | The ignition has been off for greater than 8 hours before the engine is started. |
• | The engine is running. |
• | The intake air temperature (IAT) is greater than -7°C (19°F). |
• | The engine block heater (if equipped) is not detected. |
• | The DTC runs once per cold start when the above conditions are met. |
• | The ECM detects a temperature difference on a cold start-up that indicates that the ECT sensor is 20°C (36°F) greater than the IAT sensor. |
OR |
• | The ECM detects a temperature difference on a cold start-up that indicates that the ECT sensor is 20°C (36°F) greater than the IAT sensor, and the time spent cranking the engine is greater than 10 seconds without starting, if the ECM does not detect the fuel level is low. |
DTC P0116 is a Type B DTC.
DTC P0116 is a Type B DTC.
• | Inspect the ECT sensor terminals for corrosion and for engine coolant leaking through the sensor. Engine coolant that is leaking through the sensor will create a high resistance short to ground. This condition results in less voltage on the ECT sensor signal circuit, which is interpreted by the ECM as a warmer ECT. |
• | An IAT sensor that is biased colder at various ambient temperatures due to greater resistance than is normal will increase the range between these two sensors. Measure and record the resistance of the IAT sensor at various ambient temperatures, then compare those measurements to the Temperature Versus Resistance table. |
• | Test the ECT sensor at various temperature levels in order to evaluate the possibility of a biased sensor. A sensor that is biased warmer can result in a driveability condition. Refer to Temperature Versus Resistance. |
• | If the condition is intermittent, allowing the vehicle to sit for greater than 8 hours with the ignition OFF, may help isolate the condition. Compare the scan tool RCT and ECT temperature sensor values at Ignition ON. The RCT sensor and the ECT sensor values should display within 3°C (5°F). |
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Control Module References for scan tool information
⇒ | If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle. |
Note: Depending on ambient temperature, it may take up to 4 minutes for the temperatures to equalize.
⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM. |
⇒ | If warmer than the specified value, test the signal circuit terminal 2 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.
⇒ | If less than specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM. |
Note: A thermometer can be used to the used to test the sensor off the vehicle.
⇒ | If not within the specified range, replace the ECT sensor. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for ECM replacement, setup, and programming |