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Checking the Temperature Sensors






CHECKING THE TEMPERATURE SENSORS

For a complete wiring diagram, Refer to the Wiring Information Electrical Diagrams.

1. COMPARE TEMPERATURE SENSOR VALUES
1. Turn the ignition off.
2. Allow the vehicle to sit with the ignition off in an environment where the temperature is consistent and above -7° C (19.4° F) until the engine coolant temperature is equal to ambient temperature.
3. Turn the ignition on.
4. Using a thermometer, measure and record the underhood and ambient temperatures.
5. With a scan tool, read the ambient air temperature (AAT), engine coolant temperature (ECT), engine oil temperature (EOT) and intake air temperature (IAT) sensor values, as applicable.

Are all temperature sensor values within 10° C (18° F) of the thermometer and the other sensor values?

Yes

- Test complete.

No

- Go To 2

2. TEMPERATURE SENSOR WIRING OR CONNECTORS

NOTE: Perform the following procedures for each sensor that was not within the specified range as described in the previous step.

1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the temperature sensor(s) and the applicable control module.
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals.
4. Turn the ignition on.
5. Monitor the scan tool data relative to the sensor(s) and wiggle test the wiring and connectors.
6. Look for the data to change or for a DTC to set during the wiggle test.

Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Go To 3

3. SENSOR VOLTAGE
1. Turn the ignition off.
2. Disconnect the temperature sensor harness connector.
3. Connect a jumper wire between the signal circuit and the sensor ground circuit in the sensor harness connector.
4. Turn the ignition on.
5. With a scan tool, read the sensor voltage.

NOTE: The sensor voltage should be approximately 0.0 volts (plus or minus.1 volt) with the jumper wire in place.

Does the scan tool display the voltage as described above?

Yes

- Go To 4

No

- Go To 5

4. TEMPERATURE SENSOR
1. Turn the ignition off.
2. Remove the jumper wire from between the signal circuit and the sensor ground circuit in the sensor harness connector.
3. Turn the ignition on.
4. With a scan tool, read the sensor voltage.

NOTE: The sensor voltage should be approximately 5.0 volts (plus or minus.1 of a volt) with the connector disconnected.

Does the scan tool display the voltage as described above?

Yes

- Replace the sensor.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Go To 5

5. SIGNAL CIRCUIT SHORTED TO GROUND
1. Turn the ignition off.
2. Measure the resistance between ground and the signal circuit in the sensor harness connector.

Is the resistance above 100 Ohms?

Yes

- Go To 6

No

- Repair the signal circuit for a short to ground.
- Perform the PCM Verification Test. PCM Verification Test.

6. SIGNAL CIRCUIT SHORTED TO SENSOR GROUND CIRCUIT
1. Measure the resistance between the signal circuit and the sensor ground circuit in the sensor harness connector.

Is the resistance above 100 Ohms?

Yes

- Go To 7

No

- Repair the signal circuit for a short to the sensor ground circuit.
- Perform the PCM Verification Test. PCM Verification Test.

7. SIGNAL CIRCUIT HIGH RESISTANCE
1. Turn the ignition off.
2. Connect the temperature sensor harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install PCM Pinout Box 8815 along with the Adapter 8815-1 to perform the diagnosis.

3. Using a voltmeter, perform a voltage drop test by backprobing the signal circuit at the sensor harness connector and at the applicable module connector (or by probing the appropriate terminal of the PCM Pinout Box 8815). Make sure the voltmeter leads are connected so that positive polarity is displayed on the voltmeter.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

4. Start the engine.

Is the voltage below 0.5 of a volt?

Yes

- Go To 8

No

- Repair the signal circuit for high resistance.
- Perform the PCM Verification Test. PCM Verification Test.

8. SENSOR GROUND CIRCUIT HIGH RESISTANCE
1. Turn the ignition off.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install PCM Pinout Box 8815 along with the Adapter 8815-1 to perform the diagnosis.

2. Using a voltmeter, perform a voltage drop test by backprobing the sensor ground circuit at the sensor harness connector and at the applicable module connector (or by probing the appropriate terminal of the PCM Pinout Box 8815). Make sure the voltmeter leads are connected so that positive polarity is displayed on the voltmeter.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

3. Start the engine.

Is the voltage below 0.5 of a volt?

Yes

- Go To 9

No

- Repair the sensor ground circuit for high resistance.
- Perform the PCM Verification Test. PCM Verification Test.

9. MODULE
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the sensor and the applicable control module. Refer to the system schematic.
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals.
4. Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
5. Look for the data to change or for the DTC to reset during the wiggle test.
6. Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Replace the applicable control module.
- Perform the PCM Verification Test. PCM Verification Test.

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