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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 (AAT) sensor performance looks at the outputs of three temperature sensors and compares them under cold start conditions. The AAT reading is a bussed message from the Totally Integrated Power Module (TIPM) to the Powertrain Control Module (PCM). The AAT sensor is a variable resistor that measures the ambient air temperature. The TIPM supplies a 5 volt reference and a ground to the sensors low reference signal circuit. When the AAT is low, the sensor resistance is high. When the AAT is high, the sensor resistance is low. Following a start to run delay time, the outputs of the ambient, engine coolant and intake air temperature sensors are 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, 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 the scan tool, select View DTCs.

Is the DTC Active or Pending at this time?

Yes

- Go To 3

No

- Go To 2

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 the 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

- Perform 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 the scan tool, read the AAT 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

- Go To 4

No

- Go To 5

4. AAT SENSOR




1. Turn the ignition off.
2. Connect a jumper wire between the (G31) AAT Signal circuit and the (G931) AAT Return circuit in the Ambient Air Temperature Sensor harness connector.
3. Turn the ignition on.
4. With the scan tool, read the Ambient Air Temperature Sensor voltage.

NOTE: The sensor voltage should be approximately 0.0 Volts (plus or minus.1 of a 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 Sensor and Control Module connectors. Replace the AAT Sensor if no problems were found in the connectors. Front Ambient Temperature Sensor - Removal.
- 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 C5 TIPM harness connector.
4. Start the engine and allow it to reach normal operating temperature.
5. Monitor the Voltmeter.

Is the voltage below 0.5 of a Volt?

Yes

- Go To 6

No

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

6. (G931) AAT RETURN CIRCUIT HIGH RESISTANCE
1. Turn the ignition off.
2. Using a Voltmeter perform a voltage drop test. Backprobe the (G931) AAT Return circuit at the AAT sensor harness connector and the C5 TIPM 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 of a Volt?

Yes

- Go To 7

No

- Repair the excessive resistance in the (G931) AAT Return 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 C4 TIPM 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. 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) AAT RETURN CIRCUIT




1. Measure the resistance between the (G931) AAT return 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) AAT return circuit and the (G31) AAT Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 10

10. TOTALLY INTEGRATED POWER MODULE
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the AAT Sensor and the Totally Integrated Power Module (TIPM).
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 Control Module connectors.
4. Perform any Technical Service Bulletins that may apply.

Were there any problems found?

Yes

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

No

- Replace the Totally Integrated Power Module. Totally Integrated Power Module (TIPM) - Removal.
- Perform the BODY VERIFICATION TEST Body Verification Test.

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