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  • P0071 - Ambient Air Temperature Sensor Performance

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    P0071 - Ambient Air Temperature Sensor Performance

    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:
    • Ignition on/engine off, or while the engine is running.

    Set Conditions:
    • The Powertrain Control Module (PCM) detects a fault in the Ambient Air Temperature Sensor circuit or is
    missing the signal.

    Default Actions:
    • The MIL is illuminated.

    Possible Causes

    AAT SIGNAL CIRCUIT SHORTED TO VOLTAGE
    AAT SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE
    AAT SIGNAL CIRCUIT SHORTED TO GROUND
    AAT SIGNAL CIRCUIT SHORTED TO HEATED MIRROR RETURN GROUND
    AAT SENSOR GROUND CIRCUIT OPEN OR HIGH RESISTANCE
    AMBIENT AIR TEMPERATURE (AAT) SENSOR
    DRIVERS DOOR MODULE (DDM)

    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: Diagnose any CAN C Bus Communication DTCs before continuing.
    NOTE: If there are any other DTC's related to the Engine Coolant Temperature (ECT) sensor, Charge Air
    Temperature sensor, or Intake Manifold Temperature Sensor present in the PCM perform thr
    Diagnostics for those DTCs before continuing with this one.
    1. Turn the ignition one.
    2. With the scan tool, select View DTCs. Is the DTC active?

     

    Yes
    • Go To 2

     

    No
    • Perform the INTERMITTENT DTC 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. Turn the ignition off.
    2. Disconnect the Ambient Air Temperature Sensor (AAT) harness connector.
    3. Turn the ignition on, engine not running.
    4. Measure the voltage on the (G31) AAT Signal circuit in the AAT Sensor harness connector. Is the voltage above 5.2 volts?

     

    Yes
    • Repair the (G31) AAT Signal circuit for a short to voltage.
    • Perform the PCM VERIFICATION TEST. (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. Turn the ignition off.
    2. Disconnect the Driver Door Module (DDM) C2 harness connector. 

    3. Measure the resistance of the (G31) AAT Signal circuit between the Ambient Air Temperature Sensor harness connector and the DDM C2 harness connector. Is the resistance below 5.0 Ohms?

     

    Yes
    • Go To 4

     

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

     

    4. CHECK THE (C160) HEATED MIRROR RETURN CIRCUIT FOR AN OPEN/HIGH RESISTANCE
    1. Measure the resistance of the (C160) Heated Mirror Return circuit between the Ambient Air Temperature
    Sensor harness connector and the DDM C2 harness connector.
    Is the resistance below 5.0 Ohms?

     

    Yes
    • Go To 5

     

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

     

    5. CHECK THE (G31) AAT SIGNAL CIRCUIT FOR A SHORT TO GROUND
    1. Measure the resistance between ground and the (G31) AAT Signal circuit in the AAT Sensor harness connector.
    Is the resistance above 10k Ohms?

     

    Yes
    • Go To 6

     

    No
    • Repair the (G31) AAT Signal circuit for a short to ground.

    • Perform the PCM VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

     

    6. CHECK FOR THE (G31) AAT SIGNAL CIRCUIT SHORTED TO THE (C160) HEATED MIRROR RETURN CIRCUIT
    1. Measure the resistance between the (G31) AAT Signal circuit and the (C160) Heated Mirror Return circuit
    at the AAT Sensor harness connector. Is the resistance above 10k Ohms?

     

    Yes
    • Go To 7

     

    No
    • Repair the short between the (G31) AAT Signal circuit and the (C160) Heated Mirror Return circuit.
    • Perform the PCM VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

     

    7. AMBIENT AIR TEMPERATURE SENSOR
    1. Turn the ignition off.
    2. Replace the Ambient Air Temperature Sensor in accordance with the Service Information.(Refer to 24 - Heating and Air Conditioning/Controls/SENSOR, Ambient Temperature/Removal)
    3. Turn the ignition on.
    4. With the scan tool, read DTCs. Is the DTC still reporting active or pending?

     

    Yes
    • Go To 8

     

    No
    • Repair is complete.
    • Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

     

    8. DRIVERS DOOR MODULE (DDM)

    1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the AAT Sensor and the Drivers Door Module (DDM).

    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 AAT Sensor and Drivers Door 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. (Refer to 28 - DTC-Based Diagnostics/MODULE, Body Control (BCM) /Standard Procedure).

     

    No

     • Replace the Drivers Door Module (DDM) in accordance with the Service Information.

    • Perform the BODY VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Body Control (BCM) /Standard Procedure).


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