P0072-AMBIENT AIR TEMPERATURE SENSOR CIRCUIT LOW

For a complete wiring diagram Refer to Section 8W

When Monitored:
With the ignition on and battery voltage greater than 10.4 volts.
Set Condition:
The PCM detects that the Ambient Air Temperature Sensor input voltage is below the minimum acceptable value.

Possible Causes

INTERMITTENT DTC

(G31) AAT SIGNAL CIRCUIT SHORTED TO GROUND

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

(G31) AAT SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE

AMBIENT AIR TEMPERATURE SENSOR

TOTALLY INTEGRATED POWER MODULE (TIPM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Diagnostic Test

1. DTC IS ACTIVE

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

NOTE: Diagnose and repair any system voltage DTCs before continuing with this test.

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 can result in personal injury or death.

With the scan tool, select View DTCs.

Is the status Active for this DTC?

Yes

Go to 2

Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

2. (G31) AAT SIGNAL CIRCUIT SHORTED TO GROUND

Turn the ignition off.
Disconnect the Ambient Air Temperature Sensor connector.
Disconnect the Totally Integrated Power Module (TIPM) connector.
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 3

Repair the (G31) AAT Signal circuit for a short to ground.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

3. (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 4

Repair the (G31) AAT Signal circuit for a short to the (G931) AAT Sensor Ground circuit.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

4. (G31) AAT SIGNAL CIRCUIT OPEN CIRCUIT 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 5

Repair the (G31) AAT Signal circuit for an open circuit or high resistance.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

5. AMBIENT AIR TEMPERATURE SENSOR

Turn the ignition off.
Connect the Totally Integrated Power Module (TIPM) connector.
Turn the ignition on.
With the scan tool, read the Ambient Air Temperature Sensor signal voltage.

Is the voltage above 4.5 volts with the Ambient Air Temperature Sensor harness disconnected?

Yes

Replace the Ambient Air Temperature Sensor in accordance with the service information.

Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Go to 6

6. 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.
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.
Refer to any Technical Service Bulletins that may apply.

Were any problems found?

Yes

Repair as necessary.

Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Replace and program the Totally Integrated Power Module (TIPM) in accordance with the Service Information.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).