P0071
SYMPTOM
P0071-AMBIENT AIR TEMPERATURE SENSOR PERFORMANCE
WHEN MONITORED
Engine off time is greater than 480 minutes. Ambient temperature is greater than 4 °C (38 °F).
SET CONDITION
After a calibrated amount of cool down time the PCM compares the ECT Sensor, IAT Sensor, and the Ambient Air Temp Sensor values. If the IAT Sensor value is not within -10 °C (18 °F) of the other two temperature sensors. 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. Scan Tool Testing and Procedures
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>> Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5. Powertrain Verification Test - Ver 5
2. (G31) AAT SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
Turn the ignition off.
Disconnect the C2 FCM harness connector.
Disconnect the MT Sensor harness connector.
Note: Visually inspect both the component and the PCM connectors. Look for damaged, partially broken wires, and backed out or corroded terminals.
Ignition on, engine not running.
Measure the voltage on the (G31) MT Signal circuit in the MT Sensor harness connector.
Is the voltage above 5.2 volts?
Yes>> Repair the short to voltage in the (G31) MT Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
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 MT 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) MT Signal circuit and the (G931) Sensor ground circuit in the MT Sensor harness connector.
With a scan tool, read the MT voltage.
Is the voltage below 1.0 volt with the jumper wire installed?
Yes>> Replace the MT Sensor. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
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) MT Signal circuit from the MT
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) MT Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
6. (G931) SENSOR GROUND CIRCUIT OPEN
Measure the resistance of the (G931) Sensor ground circuit from the MT 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 (NGC) POWERTRAIN VERIFICATION TEST VER-5.
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) MT Signal circuit in the MT Sensor harness connector.
Is the resistance below 100 ohms?
Yes>> Repair the short to ground in the (G31) MT Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Go To 8
8. (G31) AAT SIGNAL SHORTED TO THE (G931) SENSOR GROUND CIRCUIT
Measure the resistance between the (G31) MT Signal circuit and the (G931) Sensor ground circuit in the MT Sensor harness connector.
Is the resistance below 5.0 ohms?
Yes>> Repair the short between the (G931) Sensor ground circuit and the (G31) MT Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
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 VER-1.
No>> Replace the Front Control Module per Service Information. Perform BODY VERIFICATION TEST VER-1.