P0072-AMBIENT AIR TEMPERATURE SENSOR CIRCUIT LOW
For a complete wiring diagram Refer to Section 8W.
- When Monitored:
The ignition key on.
- Set Condition:
Ambient Temperature Sensor is less than 0.078 of a volt at the PCM for 2.8 seconds. One Trip Fault. Three good trips to turn off the MIL.
| Possible Causes |
| (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. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).
Diagnostic Test
1. AAT SENSOR VOLTAGE BELOW 0.078 OF A VOLTNOTE: Diagnose any CAN - C Communication DTCs before continuing.
Ignition on, engine not running.
With a scan tool, read the Ambient Air Temperature Sensor voltage.
Is the voltage below 0.078 of a volt?
Yes
- Go To 2
No
- Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
2. CHECKING AAT SENSOR
Turn the ignition off.
Disconnect the Ambient Air Temperature Sensor harness connector.
Ignition on, engine not running.
With a scan tool, read the AAT Sensor voltage.
Is the voltage above 4.6 volts?
Yes
- Replace the Ambient Temperature Sensor.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Go To 3
3. (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 the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Go To 4
4. (G31) AAT SIGNAL CIRCUIT SHORTED TO THE (G931) SENSOR GROUND CIRCUIT
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. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Go To 5
5. 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. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE)
No
- Replace and program the Front Control Module per Service Information.
- Perform BODY VERIFICATION TEST. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE)