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Home >> Cadillac >> 2018 >> Escalade Base, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 19 (Automatic Transmission - 6L80 (MYC) Or 6L90 (MYD) - Diagnostic Information And Procedures) >> Diagnostic Information And Procedures >> DTC P2771: Four Wheel Drive (4WD) Switch Circuit (NQF, NQH) >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different car, the 2018 GMC Yukon XL, 2018 GMC Yukon, 2018 Chevrolet Tahoe, 2018 Chevrolet Suburban 3500 HD, and 2018 Chevrolet Suburban. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition ON, transmission in Neutral, place the transfer case shift control switch in the 2 HI position.
  2. Verify the 2 high indicator light on the switch is ON and not flashing.
    • If the 2 high indicator light is flashing or is not ON 

      Refer to Circuit/System Testing.

    • Go to next step: If 2 high indicator light is ON and not flashing 
  3. Verify the scan tool TCM 4WD Low parameter displays Disabled.
    • If Disabled is not displayed 

      Refer to Circuit/System Testing.

    • Go to next step: If Disabled is displayed 
  4. Place the transfer case shift control switch in the 4 Low position.
  5. Verify the 4WD low indicator light is ON and not flashing.
    • If the 4WD low indicator light is flashing or is not ON 

      Refer to Circuit/System Testing.

    • Go to next step: If the 4WD low indicator light is ON and not flashing 
  6. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
  7. Verify the DTC does not set.
    • If the DTC sets 

      Refer to Circuit/System Testing.

    • Go to next step: If the DTC does not set 
  8. All OK.
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