P0071
P0071-AMBIENT AIR TEMPERATURE SENSOR PERFORMANCE
For a complete wiring diagram refer to: Electrical Diagrams
When Monitored
Engine off time is greater than 480 minutes. Ambient temperature is greater than 4 degrees C (38 degrees F).
Set Condition
After a calibrated amount of cool down time, the PCM compares the ECT Sensor, IAT Sensor and the Ambient Air Temperature Sensor values. If the Ambient Air Temperature Sensor value is not within a calibrated temperature amount of the other two temperature sensors an error is detected. Two Trip Fault. Three good trips to turn off the MIL.
Possible Causes
- (G31) AAT SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
- (G31) AAT SIGNAL CIRCUIT OPEN
- (G931) SENSOR GROUND CIRCUIT OPEN
- (G31) AAT SIGNAL CIRCUIT SHORTED TO GROUND
- (G31) AAT SIGNAL CIRCUIT SHORTED TO THE
- (G931) SENSOR GROUND CIRCUIT
- AMBIENT AIR TEMPERATURE SENSOR
- FRONT CONTROL MODULE
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
Diagnostic Test
1. ACTIVE DTC
NOTE: Diagnose any CAN - C Communication DTCs before continuing.
Ignition on, engine not running.
With a scan tool, read DTCs.
Is the DTC active at this time?
Yes >> Go To 2
No >> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
2. (G31) AAT SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
Turn the ignition off.
Disconnect the C2 FCM harness connector. Disconnect the AAT Sensor harness connector.
NOTE: Visually inspect both the component and the FCM connectors. Look for damaged, partially broken wires, and backed out or corroded terminals. Ignition on, engine not running. Measure the voltage on the (G31) AAT Signal circuit in the AAT Sensor harness connector.
Is the voltage above 5.2 volts?
Yes >> Repair the short to voltage in the (G31) AAT Signal circuit.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No >> Go To 3
3. AAT SENSOR VOLTAGE ABOVE 4.6 VOLTS
Turn the ignition off.
Connect the C2 FCM harness connectors.
Ignition on, engine not running.
With a scan tool, read the AAT voltage.
Is the voltage above 4.6 volts?
Yes >> Go To 4
No >> Go To 7
4. AAT SENSOR
Connect a jumper wire between the (G31) AAT Signal circuit and the (G931) Sensor ground circuit in the AAT Sensor harness connector.
With a scan tool, read the AAT voltage.
Is the voltage below 1.0 volt with the jumper wire installed?
Yes >> Replace the AAT Sensor.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No >> Go To 5
NOTE: Remove the jumper wire before continuing.
5. (G31) AAT SIGNAL CIRCUIT OPEN
Turn the ignition off.
Disconnect the C2 FCM harness connector.
Measure the resistance of the (G31) AAT Signal circuit from the AAT Sensor harness connector to the C2 FCM harness connector.
Is the resistance below 5.0 ohms?
Yes >> Go To 6
No >> Repair the open in the (G31) AAT Signal circuit.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
6. (G931) SENSOR GROUND CIRCUIT OPEN
Measure the resistance of the (G931) Sensor ground circuit from the AAT Sensor harness connector to the C2 FCM harness connector.
Is the resistance below 5.0 ohms?
Yes >> Go To 9
No >> Repair the open in the (G931) Sensor ground circuit.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
7. (G31) AAT SIGNAL CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect the C2 FCM harness connector.
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 POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No >> Go To 8
8. (G31) AAT SIGNAL SHORTED TO THE (G931) SENSOR GROUND CIRCUIT
Measure the resistance between the (G31) AAT Signal circuit and the (G931) Sensor ground 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 POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No >> Go To 9
9. FRONT CONTROL MODULE
NOTE: Before continuing, check the FCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
Were there any problems found?
Yes >> Repair as necessary
Perform BODY VERIFICATION TEST Body Verification Test
No >> Replace the Front Control Module per Service Information.
Perform BODY VERIFICATION TEST Body Verification Test