NGC

P0071-AMBIENT AIR TEMPERATURE SENSOR PERFORMANCE





For a complete wiring diagram Consult Diagrams/Electrical

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.Initial Inspection and Diagnostic Overview

Diagnostic Test

1. DTC IS ACTIVE

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

Turn the ignition off.
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).
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.
With a 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
Turn the ignition off.
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.
Turn the ignition on.
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 *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure.Checking For An Intermittent DTC

No

- Go to 3

3. (G31) AAT SIGNAL CIRCUIT SHORTED TO VOLTAGE




Turn the ignition off.
Disconnect the Ambient Air Temperature Sensor connector.
Disconnect the C4 Totally Integrated Power Module (TIPM) connector.
Turn the ignition on.
Measure the voltage of the (G31) AAT Signal circuit in the Ambient Air Temperature Sensor harness connector.
Is there any voltage present?

Yes

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

No

- Go to 4

4. (G31) AAT SIGNAL CIRCUIT SHORTED TO GROUND




Turn the ignition off.
Measure the resistance between ground and the (G31) AAT Signal circuit in the Ambient Air Temperature Sensor harness connector.
Is the resistance above 100 ohms?

Yes

- Go to 5

No

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

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




Measure the resistance between the (G31) AAT Signal circuit and the (G931) AAT Sensor Ground circuit in the Ambient Air Temperature Sensor harness connector.
Is the resistance above 100 ohms?

Yes

- Go to 6

No

- Repair the short between the (G31) AAT Signal circuit and the (G931) AAT Sensor Ground circuit.
- Perform the PCM Verification Test. Powertrain Verification Test

6. (G31) AAT SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE




Measure the resistance of the (G31) AAT Signal circuit between the Ambient Air Temperature Sensor harness connector and the Totally Integrated Power Module (TIPM) harness connector.
Is the resistance below 5.0 ohms?

Yes

- Go to 7

No

- Repair the open or high resistance in the (G31) AAT Signal circuit.
- Perform the PCM Verification Test. Powertrain Verification Test

7. (G931) AAT SENSOR GROUND CIRCUIT OPEN OR HIGH RESISTANCE




Measure the resistance of the (G931) AAT Sensor Ground circuit between the Ambient Air Temperature Sensor harness connector and the Totally Integrated Power Module (TIPM) harness connector.
Is the resistance below 5.0 ohms?

Yes

- Go to 8

No

- Repair the open or high resistance in the (G931) AAT Sensor Ground.
- Perform the PCM Verification Test. Powertrain Verification Test

8. AMBIENT AIR TEMPERATURE SENSOR




Turn the ignition off.
Connect the Totally Integrated Power Module (TIPM) connector.
Connect a jumper wire between the (G931) AAT Sensor Ground circuit and the (G31) AAT Signal circuit in the Ambient Air Temperature Sensor harness connector.
Turn the ignition on.
With the scan tool, read the Ambient Air Temperature Sensor signal voltage.
Is the voltage below 1.0 volt with the jumper wire in place?

Yes

- Verify that there is good pin to terminal contact in the AAT Sensor and Totally Integrated Power Module connectors. Replace the AAT Sensor if no problems were found with the connectors.
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Go to 9

9. TOTALLY INTEGRATED POWER MODULE (TIPM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Ambient Air Temperature Sensor and the Totally Integrated Power Module (TIPM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Verify that there is good pin to terminal contact in the AAT Sensor and TIPM connectors.
Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
Look for the data to change or for the DTC to reset during the wiggle test.
Search for any Technical Service Bulletins that may apply.
Were any problems found?

Yes

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

No

- Replace the Totally Integrated Power Module (TIPM).
- Perform the PCM Verification Test. Powertrain Verification Test