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P0071






P0071-AMBIENT AIR TEMPERATURE SENSOR PERFORMANCE





For a complete wiring diagram Refer to the Wiring Information.

Theory of Operation

Ambient Air Temperature Sensor performance looks at the outputs of three temperature sensors and compares them under cold start conditions. Following a start to run delay time, the outputs of the ambient, engine coolant, and intake air temperature sensors will be compared. If the engine coolant and intake air temperature sensors agree and the ambient air temperature does not agree, the ambient air temperature sensor is declared as irrational. If declared irrational a second comparison will be done after a short drive cycle.

- When Monitored:
Engine off time is greater than 480 minutes and the vehicle has been driven for one minute over 35 mph. Ambient temperature is greater than -64° C (-83° F).

- Set Condition:
The PCM compares the ambient, engine coolant, and intake air temperature sensor values. If engine coolant and intake air temperature sensors agree with each other but ambient air temperature does not agree with them, the ambient air temperature sensor is declared as irrational. Two Trip Fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DTC

NOTE: Diagnose any CAN - C Communication DTCs before continuing.

1. Turn the ignition off.
2. If possible, allow the vehicle to sit with the ignition off for more than 480 minutes in an environment where the temperature is consistent and above -7° C (19.4° F).
3. Test drive the vehicle. The vehicle must exceed 48 km/h (30 mph) during the test drive. Do not cycle the ignition off when the test drive is completed.
4. With a scan tool, select View DTCs.

Is the DTC Active or Pending at this time?

Yes

- Go To 3

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition Test.

2. AMBIENT AIR TEMPERATURE
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. With a scan tool, compare the AAT, ECT, and IAT sensor values.

Is the Ambient Air Temperature Sensor value within 10° C (18° F) of the other two sensor values?

Yes

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition Test

No

- Go To 3

3. AAT SENSOR VOLTAGE
1. Turn the ignition off.
2. Disconnect the AAT sensor harness connector.
3. Ignition on, engine not running.
4. With a scan tool, read the AAT voltage.

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

Does the scan tool display the voltage as described above?

Yes

- Go To 4

No

- Go To 5

4. AAT SENSOR




1. Connect a jumper wire between the (G31) AAT Signal circuit and the (G931) Sensor Ground circuit in the Ambient Air Temperature Sensor harness connector.
2. With a scan tool, read the Ambient Air Temperature 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

- Verify that there is good pin to terminal contact in the Ambient Air Temperature Sensor and Front Control Module connectors. If OK, replace the AAT Sensor.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 5
NOTE: Remove the jumper wire before continuing.

5. (G31) AAT SIGNAL CIRCUIT HIGH RESISTANCE
1. Turn the ignition off.
2. Reconnect the AAT sensor harness connector.
3. Using a voltmeter perform a voltage drop test. Backprobe the (G31) AAT Signal circuit at the AAT Sensor harness connector and the C2 FCM harness connector.

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 and allow it to reach normal operating temperature.
5. Monitor the voltmeter.

Is the voltage below 0.5 volts?

Yes

- Go To 6

No

- Repair the high resistance in the (G31) AAT Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

6. (G931) SENSOR GROUND CIRCUIT HIGH RESISTANCE
1. Turn the ignition off.
2. Using a voltmeter perform a voltage drop test. Backprobe the (G931) Sensor ground circuit at the AAT Sensor harness connector and the C2 FCM harness connector.

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 and allow it to reach normal operating temperature.
4. Monitor the voltmeter.

Is the voltage below 0.5 volts?

Yes

- Go To 7

No

- Repair the high resistance in the (G931) Sensor ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

7. (G31) AAT SIGNAL CIRCUIT SHORTED TO VOLTAGE




1. Turn the ignition off.
2. Disconnect the C2 FCM harness connector.
3. Ignition on, engine not running.
4. Measure the voltage on the (G31) AAT Signal circuit in the AAT Sensor harness connector.

Is there any voltage present?

Yes

- Repair the short to voltage in the (G31) AAT Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 8

8. (G31) AAT SIGNAL CIRCUIT SHORTED TO GROUND




1. Turn the ignition off.
2. Disconnect the C2 FCM harness connector.
3. Measure the resistance between ground and the (G31) AAT Signal circuit in the AAT Sensor harness connector.

Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (G31) AAT Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 9

9. (G31) AAT SIGNAL CIRCUIT SHORTED TO THE (G931) SENSOR GROUND CIRCUIT




1. Measure the resistance between the (G931) Sensor ground circuit and the (G31) AAT Signal circuit in the AAT Sensor harness connector.

Is the resistance below 5.0 ohms?

Yes

- Repair the short between the (G931) Sensor ground circuit and the (G31) AAT Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 10

10. FRONT CONTROL MODULE (FCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the AAT Sensor and the Front Control Module (FCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Sensor and Front Control Module connectors.
4. Search for any Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform BODY VERIFICATION TEST. Body Verification Test.

No

- Replace the Front Control Module.
- Perform BODY VERIFICATION TEST. Body Verification Test.

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