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Home >> Chevrolet >> 2016 >> Suburban 3500 HD LT >> Repair and Diagnosis >> Transmission >> Transfer Case >> Transfer Case - Mp 3023/3024 (NQH) - Diagnostic Information And Procedures >> Diagnostic Information and Procedures >> DTC P185F or P279A-P279C: Transfer Case Range / Four Wheel Drive (4WD) Neutral Range (L83) >> Circuit/System Verification

Circuit/System Verification

NOTE:

Please first be sure to review the Diagnostic Aids before continuing further.

  1. Ignition » On / Vehicle » In Service Mode & Engine » Off
  2. Verify DTC P0502, P0503, P0721, P0722, P0723, P077C, P077D, P2160, P2161 is not set. is not set.
    • If none of the DTCs are set 
  3. Ignition On - Engine Running & Greater than 1 min
    4. NOTE:

    It may take up to 2 min for all vehicle systems to power down.

  4. Ignition/Vehicle Off, key out of the ignition/keyless start transmitter 1 m (3 ft) from the vehicle, and all vehicle systems Off.

    - Greater than 2 min

  5. Ignition » On / Vehicle » In Service Mode & Engine » Off
  6. Verify DTC P17D4, P185F, P279A, P279B, P279C is only set as a history DTC.
    • If any of the DTCs are set as current.  Refer to: Circuit/System Testing
    • If any of the DTCs are only set as history.  Refer to Diagnostic Aids before proceeding with Circuit/System Testing.
    • If none of the DTCs are set 
  7. Clear All Vehicle DTCs
  8. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
  9. When operating the vehicle within the Conditions for Running the DTC, monitor the following parameters (they should match each other and show a smooth/steady curve when viewed in graph form):
    • Transmission OSS
    • Transfer Case OSS(K20)/B115Vehicle Speed Sensor(Transfer Case Control Schematics)
    • If the above parameters do not match or are not smooth 

      Refer to: Diagnostic Trouble Code (DTC) List - Vehicle DTC P0720/P722 for Transmission OSS or DTC P2160/P2161 for Transfer Case OSS(K20)/B115 Vehicle Speed Sensor(Transfer Case Control Schematics)

    • If the above parameters match and are smooth 
  10. Verify DTC P17D4, P185F, P279A, P279B, P279C is not set.
    • If the DTC is set 

      Refer to: Circuit/System Testing

    • If the DTC is not set 
  11. All OK.
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