Engine Coolant Temperature Sensor

Engine Coolant Temperature Sensor Circuit:

WHEN MONITORED
With the ignition on.

SET CONDITION
The A/C Heater Control Module reports an abnormally high or low voltage that is detected by the Instrument Cluster. The abnormal condition is at the Powertrain Control Module (PCM) on the Engine Coolant Temperature Sensor Signal circuit. The abnormal condition is communicated from the PCM to the Instrument Cluster by the CAN bus.

POSSIBLE CAUSES
- Engine coolant temperature sensor signal circuit short to voltage
- Engine coolant temperature sensor open
- Engine coolant temperature sensor signal circuit open
- Engine coolant temperature sensor ground open
- Engine coolant temperature sensor signal circuit short to ground
- Powertrain control module

Diagnostic Test




1. READ ENGINE COOLANT TEMPERATURE SENSOR VOLTAGE WITH DRB III(R)

Turn the ignition on.
With the DRB III(R), read the Engine Coolant Temperature Sensor voltage.

Q: Does the DRB III(R) display ENGINE COOLANT TEMP: 5.0 VOLTS or greater?

YES: Go to 2
NO: Go to 6




2. MEASURE THE VOLTAGE OF THE ENGINE COOLANT TEMPERATURE SENSOR SIGNAL CIRCUIT

Turn the ignition off.
Disconnect the Engine Coolant Temperature Sensor harness connector.

NOTE: Check connector - Clean/repair as necessary.
Turn the ignition on.

Measure the voltage of the Engine Coolant Temperature Sensor Signal Circuit at the Engine Coolant Temperature Sensor harness connector.

Q: Is the voltage above 5.5 volts?

YES: Repair the Engine Coolant Temperature Sensor Signal circuit for a short to voltage. Perform BODY VERIFICATION TEST. Body Verification Test
NO: Go to 3




3. READ ENGINE COOLANT TEMPERATURE SENSOR VOLTAGE WITH DRB III(R)

Turn the ignition off.
Connect a jumper wire between the Engine Coolant Temperature Sensor
Signal circuit and the Sensor Ground circuit.
Turn the ignition on.
With the DRB III(R), read the Engine Coolant Temperature Sensor voltage.

Q: Does the DRB III(R) display ENGINE COOLANT TEMP: 4.5 VOLTS or greater?

YES: Go to 4
NO: Replace the Engine Coolant Temperature Sensor.Perform BODY VERIFICATION TEST.




4. MEASURE THE RESISTANCE OF THE ENGINE COOLANT TEMPERATURE SENSOR SIGNAL CIRCUIT

Turn the ignition off.
Disconnect the Powertrain Control Module harness connector.

NOTE: Check connector - Clean/repair as necessary. Measure the resistance of the Engine Coolant Temperature Sensor Signal circuit from the Powertrain Control Module harness connector to the Engine Coolant Temperature Sensor harness connector.

Q: Is the resistance below 5.0 ohms?

YES: Go to 5
NO: Repair the Engine Coolant Temperature Sensor Signal circuit for an open. Perform BODY VERIFICATION TEST. Body Verification Test




5. MEASURE THE RESISTANCE OF THE SENSOR GROUND CIRCUIT

With the ignition off.
Measure the resistance of the Sensor Ground circuit from the Powertrain Control Module harness connector to the Engine Coolant Temperature Sensor harness connector.

Q: Is the resistance below 5.0 ohms?

YES: Replace the Powertrain Control Module.Perform BODY VERIFICATION TEST. Body Verification Test
NO: Repair the Sensor Ground circuit for an open.Perform BODY VERIFICATION TEST. Body Verification Test




6. READ ENGINE COOLANT TEMPERATURE SENSOR VOLTAGE WITH DRB III(R)

Turn the ignition off.
Disconnect the Engine Coolant Temperature Sensor harness connector.

NOTE: Check connector - Clean/repair as necessary.
Turn the ignition on.
With the DRB III(R), read the Engine Coolant Temperature Sensor voltage.

Q: Does the DRB III(R) display ENGINE COOLANT TEMP: 4.5 VOLTS or greater?

YES: Go to 7
NO: Go to 9




7. READ A/C HEATER CONTROL MODULE DTC'S WITH DRB III(R)

Turn the ignition off.
Reconnect the Engine Coolant Temperature Sensor connector.
Turn the ignition on.
With the DRB III(R), read A/C Heater Control Module DTC's.
Wait two minutes.
With the DRB III(R), read A/C Heater Control Module DTC's.

Q: Does the DRB III(R) display an Engine Coolant Temperature Sensor Failure DTC?

YES: Replace the Engine Coolant Temperature Sensor. Perform BODY VERIFICATION TEST. Body Verification Test
NO: Go to 8




8. READ A/C HEATER CONTROL MODULE DTC'S WITH DRB III(R)

Ensure the Engine Coolant Temperature Sensor is connected at this time.
Start the engine.
Turn the A/C system on and run for at least five minutes.
With the DRB III(R), read A/C Heater Control Module DTC's.

Q: Does the DRB III(R) display an Engine Coolant Temperature Sensor Failure DTC?

YES: Replace the Engine Coolant Temperature Sensor. Perform BODY VERIFICATION TEST. Body Verification Test
NO: The condition that caused this DTC to set is currently not present. Inspect the related wiring harness for a possible intermittent condition. Perform BODY VERIFICATION TEST. Body Verification Test




9. MEASURE THE RESISTANCE BETWEEN GROUND AND THE ENGINE COOLANT TEMPERATURE SENSOR SIGNAL CIRCUIT

Turn the ignition off.
Disconnect the Powertrain Control Module harness connector.

NOTE: Check connector - Clean/repair as necessary. Measure the resistance between ground and the Engine Coolant Temperature Signal circuit at the Powertrain Control Module connector.

Q: Is the resistance below 1000.0 ohms?

YES: Repair the Engine Coolant Temperature Sensor Signal circuit for a short to ground. Perform BODY VERIFICATION TEST. Body Verification Test
NO: Go to 10




10. MEASURE THE RESISTANCE FROM THE ENGINE COOLANT TEMPERATURE SENSOR SIGNAL CIRCUIT TO THE SENSOR GROUND CIRCUIT

With the ignition off.
Measure the resistance from the Engine Coolant Temperature Sensor Signal circuit to the Sensor Ground circuit at the Engine Coolant Temperature Sensor harness connector.

Q: Is the resistance below 1000.0 ohms?

YES: Repair the Engine Coolant Temperature Sensor Signal circuit for a short to the Sensor Ground circuit. Perform BODY VERIFICATION TEST. Body Verification Test
NO: Replace the Powertrain Control Module. Perform BODY VERIFICATION TEST. Body Verification Test