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HOMESERVICE MANUALSFORD2021TRANSIT-350 HD BASE, VAN CARGO EXTENDED, 3.5L ENG VIN 8, AWDREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - PINPOINT TESTS (EXCEPT DIESEL & HYBRID) (A TO H)PINPOINT TESTS FA: AMBIENT AIR TEMPERATURE (AAT) SENSORTEST PROCEDURE
2021 Ford Transit-350 HD Base, Van Cargo Extended, 3.5L Eng VIN 8, AWD

Test Procedure

2021 Ford Transit-350 HD Base, Van Cargo Extended, 3.5L Eng VIN 8, AWDSECTION Test Procedure
  1. FA1 CHECK FOR DTCS 

    Are DTCs P0071, P0072, P0073 or P0074 present? 

    Yes No
    GO to  FA2 RETURN to Symptom Charts for further direction.
  2. FA2 CHECK FOR AN OPEN 
    • Ignition OFF.
    • AAT Sensor connector disconnected.
    • PCM connector disconnected.
    • Measure the resistance between:
      (+) AAT Sensor Connector, Harness Side (-) PCM Connector, Harness Side
      AAT AAT
      SIGRTN SIGRTN

    Are the resistances less than 5 ohms? 

    Yes No
    GO to  FA3 REPAIR the open circuit. Clear the PCM DTCs.
    REPEAT the self-test.
  3. FA3 CHECK FOR A SHORT 
    • Measure the resistance between:
      (+) AAT Sensor Connector, Harness Side (-)
      AAT Ground
    • Measure the resistance between:
      (+) AAT Sensor Connector, Harness Side (-) AAT Sensor Connector, Harness Side
      AAT SIGRTN

    Is the resistance greater than 10K ohms? 

    Yes No
    GO to  FA4 REPAIR the short circuit. Clear the PCM DTCs.
    REPEAT the self-test.
  4. FA4 CHECK FOR A SHORT TO VOLTAGE 
    • Ignition ON, engine OFF.
    • Measure the voltage between:
      (+) AAT Sensor Connector, Harness Side (-)
      AAT Ground
      SIGRTN Ground

    Is any voltage present? 

    Yes No
    REPAIR the short circuit. Clear the PCM DTCs.
    REPEAT the self-test.    		 GO to  FA5
  5. FA5 INTERMITTENT CHECK 
    • Ignition OFF.
    • PCM connector connected.
    • AAT Sensor connector connected.
    • Ignition ON, engine OFF.
    • Access the PCM and monitor the AAT_V (VOLT) PID.
    • While observing the PID, carry out the following:
      • Wiggle the harness from the sensor to the module.
      • Wiggle the connectors and make sure they seat correctly.
      • Look for sudden changes in the PID value when the harness and connector are wiggled.

    Is a concern present? 

    Yes No
    REPAIR as necessary.
    Clear the PCM DTCs. REPEAT the self-test.    		 GO to  FA6
  6. FA6 CHECK THE RESISTANCE OF THE AAT SENSOR 
    NOTE: Verify the external temperature of the sensor is at ambient temperature. Refer to the Ambient Air Temperature (AAT) Sensor  Expected Values chart for the temperature and resistance values.
    • Ignition OFF.
    • AAT Sensor connector disconnected.
    • Measure the resistance between:
      (+) AAT Sensor Connector, Component Side (-) AAT Sensor Connector, Component Side
      AAT SIGRTN

    Is the resistance within specification? 

    Yes No
    The system is operating correctly at this time.
    The concern may have been caused by a loose or corroded connector.    		 INSTALL a new AAT sensor. REFER to the appropriate Service Information article.
    RESET the keep alive memory (KAM). Refer to Resetting The Keep Alive Memory (KAM).
    Clear the PCM DTCs. REPEAT the self-test.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.