P0073

P0073-AMBIENT AIR TEMPERATURE SENSOR CIRCUIT HIGH

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

Ambient Air Temperature (AAT) sensor performance looks at the outputs of three temperature sensors and compares them under cold start conditions. The AAT reading is a bussed message from the Body Control Module (BCM) to the Powertrain Control Module (PCM). Following a start to run delay time, the outputs of the ambient, engine coolant and intake air temperature sensors are compared. The AAT sensor is a variable resistor that measures the ambient air temperature. The BCM supplies a 5 Volt reference and a ground to the sensors low reference signal circuit. When the AAT is low, the sensor resistance is high. When the AAT is high, the sensor resistance is low.

- When Monitored:
With the ignition on. Battery voltage greater than 10 Volts.

- Set Condition:
The Ambient Temperature Sensor voltage is greater than the maximum acceptable value. One Trip Fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DTC

NOTE: Diagnose any CAN - C Communication DTCs in the PCM or Ambient Air Temperature Sensor DTCs in the BCM before continuing.

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. With the scan tool, select View DTCs.

Is the DTC Active at this time?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

2. AAT SENSOR
1. Turn the ignition off.
2. Disconnect the Ambient Air Temperature Sensor harness connector.
3. Ignition on, engine not running.
4. With the scan tool, read AAT Sensor voltage.
5. Connect a jumper wire between the AAT Signal circuit and the AAT Return circuit in the AAT Sensor harness connector.

NOTE: The sensor voltage should be approximately 0.0 Volts (plus or minus.1 of a Volt) with the jumper wire in place.

Does the scan tool display the voltage as described above?

Yes

- Verify that there is good pin to terminal contact in the Sensor and Control Module connectors. Replace the Ambient Air Temperature Sensor if no problems were found with the connectors.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 3
NOTE: Remove the jumper wire before continuing.


3. AAT SIGNAL CIRCUIT SHORTED TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the BCM harness connector.
3. Ignition on, engine not running.
4. Measure the voltage on the AAT Signal circuit in the AAT Sensor harness connector.

Is there any voltage present?

Yes

- Repair the short to voltage in the AAT Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 4

4. AAT SIGNAL CIRCUIT OPEN
1. Turn the ignition off.
2. Measure the resistance of the AAT Signal circuit from the AAT Sensor harness connector to the BCM harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 5

No

- Repair the open in the AAT Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

5. AAT RETURN CIRCUIT OPEN
1. Measure the resistance of the AAT Return circuit from the AAT Sensor harness connector to the BCM harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 6

No

- Repair the open in the AAT Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

6. BODY CONTROL MODULE (BCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the AAT Sensor and the Body Control Module (BCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Sensor and Control Module connectors.
4. Perform any Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the BODY VERIFICATION TEST. Body Verification Test.Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Body Control Module (BCM). Body Control Module - Removal.
- Perform the BODY VERIFICATION TEST. Body Verification Test.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.