Circuit/System Testing

WARNING: This page is about a different car, the 2017 GMC Yukon XL, 2017 GMC Yukon, 2017 Chevrolet Tahoe, and 2017 Chevrolet Suburban. However, it is still accessible from the selected car via links, so may be relevant.

Ignition ON/Vehicle in Service Mode
Clear All Vehicle DTCs.
Operate the vehicle within the Conditions for Running the DTC.
Verify the DTC does not set.
- If the DTC sets
  Program the ECM.
  
  Refer to:Transfer Case Assembly Replacement
- Operate the vehicle within the Conditions for Running the DTC.
- Verify the DTC does not set.
  If the DTC sets
  
  Replace the component:K20 Engine Control Module
  
  If the DTC does not set
  
  All Ok.
- If the DTC does not set
Using the transfer case range selection switch, shift the transfer case between 2HI, 4HI, 4LO, and Neutral, allowing enough time between each selection for the transfer case to complete each shift. During each selection, verify the scan tool Transfer Case Range Selection Switch State parameter and the Transfer Case Commanded Position parameter match and that the appropriate indicator on the transfer case range selection switch illuminates, indicating the transfer case has completed the shift.
- If the transfer case does not operate as specified
  Inspect the transfer case assembly for any electrical or mechanical condition that would inhibit shifting.
- If the transfer case does not operate as specified
Refer to Diagnostic Aids. Drive the vehicle and ensure there is no slippage in the transfer case clutch.