Circuit/System Testing

Monitor the scan tool parameter:4WD Low Range Indicator Command
Operate the component:S77 Transfer Case Shift Control Switch& 4WD Low
Verify the scan tool parameter:4WD Low Range Indicator Command=On
- If the parameter does not display the following: On
  Repair or replace the component: Transfer Case Assembly
  
  Refer to:Transfer Case Assembly Replacement
- If the parameter displays the following: On
Operate the component:S77 Transfer Case Shift Control Switch - 2WD
Verify the scan tool parameter:4WD Low Range Indicator Command = Off
- If the parameter does not display the following: Off
  Repair or replace the component: Transfer Case Assembly
  
  Refer to:Transfer Case Assembly Replacement .
- If the parameter displays the following: Off
Operate the component:S77 Transfer Case Shift Control Switch - 4WD High/Locked
Verify the scan tool parameter:4WD Low Range Indicator Command =Off
- If the parameter does not display the following: Off
  Repair or replace the component: Transfer Case Assembly
  
  Refer to:Transfer Case Assembly Replacement .
- If the parameter displays the following: Off
Operate the component:S77 Transfer Case Shift Control Switch - Neutral
Verify the scan tool parameter:4WD Low Range Indicator Command =Off
- If the parameter does not display the following: Off
  Repair or replace the component: Transfer Case Assembly
  
  Refer to:Transfer Case Assembly Replacement .
- If the parameter displays the following: Off
Clear DTCs
Operate the vehicle within the Conditions for Running the DTC.
Verify the DTC does not set.
- If the DTC sets
1. Program the ECM.
2. Operate the vehicle within the Conditions for Running the DTC.
3. Verify the DTC does not set.
  - If the DTC set
    Replace the component:K20 Engine Control Module
  1. Program the ECM.
  2. Operate the vehicle within the Conditions for Running the DTC.
  3. Verify the DTC does not set.
    - If the DTC sets
      Repair or replace as necessary - Transfer Case
- If the DTC does not set
All OK.