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  • P0073 - Ambient Air Temperature Sensor S

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    P0073 - Ambient Air Temperature Sensor Circuit High

    Theory of Operation

    The Ambient Air Temperature (AAT) Sensor is located in the driver's door mirror. The Driver's Door Module (DDM) receives the data from the AAT sensor and sends it to the Body Control Module (BCM). The BCM then passes the data on to the Powertrain Control Module (PCM). There are two rationality tests. The first test is: Ignition on/engine running. The second test is: After an eight hour cold soak, at key on the readings for the AAT, Charge Air Cooler (CAC) temperature (D2, DJ), Intake Manifold Temperature (DD, DP), and the Engine Coolant Temperature (ECT) Sensors are all compared. If the temperatures differ by more than a calibrated amount, then the appropriate sensor fault code would be recorded. The PCM rationality check looks at the temperature reading from the sensor over time and ensures that it changes with the engine running. If the sensor reading does not change over a calibrated time limit, the fault will be recorded.

    When Monitored and Set Conditions

    When Monitored: This diagnostic runs continuously when the following conditions are met:
    • With the ignition on.

    Set Conditions:
    • The Powertrain Control Module (PCM) detects that the Ambient Air Temperature (AAT) Signal circuit value is above a calibrated threshold.

    Default Actions:
    • The MIL is illuminated.

    Possible Causes

    AAT SENSOR SIGNAL CIRCUIT OPEN/HIGH RESISTANCE
    AAT SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE
    DRIVER MIRROR HEATER RETURN CIRCUIT OPEN/HIGH RESISTANCE
    AMBIENT AIR TEMPERATURE (AAT) SENSOR

    Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTCBased Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

    Diagnostic Test

    1. ACTIVE DTC

     

    NOTE: There is no direct circuit input from the Ambient Air Temperature Sensor to the PCM. If there are any Loss of Communication DTCs related to the DDM present in the Body Control Module or elsewhere, perform those diagnostics before continuing with this diagnostic tree.

     

    NOTE: If there are any other DTCs related to the Ambient Air Temperature Sensor present in the BCM, DDM, or any other module, perform those diagnostics before continuing with this diagnostic tree.

     

    1. Turn the ignition on.
    2. With the scan tool, record all Freeze frame data.
    3. With the scan tool, erase DTCs.
    4. Turn the ignition off for 75 seconds.
    5. Turn the ignition on.
    6. With the scan tool, read DTCs.
    Did DTC P073 reset?

     

    Yes
    • Go To 2

     

    No
    • Perform the INTERMITTENT CONDITION diagnostic procedure. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

     

    2. CHECK THE (G31) AAT SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE
    1. Disconnect the AAT Sensor harness connector.
    2. Measure the voltage of the (G31) AAT Signal circuit at the AAT Sensor harness connector.
    NOTE: The voltage should read approximately 5.0 Volts with connector disconnected and key on.

    Is the voltage above 5.2 Volts?

     

    Yes
    • Repair the (G31) Ambient Air Temperature Signal circuit for a short to voltage.
    • Perform the POWERTRAIN VERIFICATION TEST - 6.7L. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

     

    No
    • Go To 3
    3. CHECK THE (G31) AAT SIGNAL CIRCUIT FOR AN OPEN/HIGH RESISTANCE

    1. Disconnect the DDM harness connector.
    2. Measure the resistance of the (G31) AAT Signal circuit between the AAT Sensor harness connector and the DDM harness connector.
    Is the resistance below 5.0 Ohms?

     

    Yes
    • Go To 4

     

    No
    • Repair the (G31) Ambient Air Temperature Signal circuit for an open or high resistance.
    • Perform the POWERTRAIN VERIFICATION TEST - 6.7L. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

     

    4. CHECK THE (C160) DRIVER MIRROR HEATER RETURN CIRCUIT FOR AN OPEN/HIGH RESISTANCE

     

    1.
    2. Measure the resistance of the (C160) Driver Mirror Heater Return circuit between the ECT Sensor harness
    connector and the PCM C1 harness connector.
    Is the resistance below 5.0 Ohms?

     

    Yes
    • Replace the Ambient Air Temperature Sensor in accordance with the Service Information.(Refer to 24 - Heating and Air Conditioning/Controls/SENSOR, Ambient Temperature/Removal)
    • Perform the POWERTRAIN VERIFICATION TEST - 6.7L. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

     

    No
    • Repair the (C160) Driver Mirror Heater Return circuit for an open or high resistance.
    • Perform the POWERTRAIN VERIFICATION TEST - 6.7L. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).


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