Powertrain Control Module (PCM)
P0072-AMBIENT AIR TEMPERATURE SENSOR CIRCUIT LOW
For a complete wiring diagram, refer to the Wiring Information Electrical Diagrams.
- When Monitored:
The ignition key on.
- Set Condition:
Ambient Temperature (AAT) sensor is less than 0.078 of a Volt at the Powertrain Control Module (PCM) for 2.8 seconds. One Trip Fault. Three good trips to turn off the Malfunction Indicator Lamp (MIL).
WARNING: On vehicles equipped with the high voltage system, you must thoroughly read and follow all High Voltage Safety procedures. In addition, before performing any diagnostic or service procedure near a high voltage component, you must perform the High Voltage Power Down. Failure to follow these instructions may result in possible serious or fatal injury
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.Pre-Diagnostic Troubleshooting Procedure.
1. Diagnostic Trouble Code (DTC) IS ACTIVE
1. Start the engine and allow it to reach normal operating temperature.
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.
NOTE: Diagnose and repair any system voltage DTCs before continuing with this test.
2. Using the scan tool, select View DTCs.
Is the DTC active at this time?
Yes
- Go To 2
No
- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition Test.
2. CHECKING AAT SENSOR
1. Turn the ignition off.
2. Disconnect the AAT sensor electrical connector.
3. Ignition on, engine not running.
4. Using the scan tool, read the AAT sensor voltage.
NOTE: The sensor voltage should be approximately 5 Volts (plus or minus 0.1 volt) with the connector disconnected.
Does the scan tool display the voltage as described above?
Yes
- Verify there is good pin to terminal contact in the AAT sensor and Front Control Module (FCM) electrical connectors. Replace the AAT sensor if no problems were found with the connectors.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 3
3. (G31) AAT SIGNAL CIRCUIT SHORTED TO GROUND
1. Turn the ignition off.
2. Disconnect the FCM C2 electrical connector.
3. Measure the resistance between ground and the (G31) AAT signal circuit in the AAT sensor electrical connector.
Is the resistance less than100 ohms?
Yes
- Repair the short to ground in the (G31) AAT signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 4
4. (G31) AAT SIGNAL CIRCUIT SHORTED TO THE (G931) SENSOR GROUND CIRCUIT
1. Measure the resistance between the (G931) sensor ground circuit and the (G31) AAT signal circuit in the AAT sensor electrical connector.
Is the resistance less than 5.0 ohms?
Yes
- Repair the short between the (G931) sensor ground circuit and the (G31) AAT signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 5
5. EXCESSIVE RESISTANCE IN THE (G31) AAT SIGNAL CIRCUIT
1. Measure the resistance of the (G31) AAT signal circuit between the AAT sensor electrical connector and the FCM C2 electrical connector.
Is the resistance less than 5ohms?
Yes
- Go To 6
No
- Repair the excessive resistance in the (G31) AAT signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
6. FRONT CONTROL MODULE (FCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the AAT sensor and the FCM.
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify there is good pin to terminal contact in the AAT sensor and FCM electrical.
4. Search for any Technical Service Bulletins (TSBs) that may apply.
Were there any problems found?
Yes
- Repair as necessary.
- Perform BODY VERIFICATION TEST VER - 1. Body Verification Test.
No
- Replace and program the FCM.
- Perform BODY VERIFICATION TEST VER - 1. Body Verification Test.