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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1435 (Transfer Case - NVG 226-NP8) >> Diagnostic Information and Procedures >> Transfer Case Shift Control Switch Inoperative >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 2:  This step tests the functionality of the mode switch.
  2. 3:  This step tests the modules ability to operate the transfer case modes.
Transfer Case Shift Control Switch Inoperative

Step Action Yes No
1
IMPORTANT: If the transfer case shift control switch is left between the 4HI and 4LO mode detents, the transfer case defaults to AWD mode. This is considered a characteristic of the system. Ensure the switch is within the proper detents.
Did you perform the Diagnostic System Check - Transfer Case?		 Go to Step 2  Go to Diagnostic System Check - Transfer Case 
2 
  1. Install a scan tool.
  2. Start the engine.
  3. Place the transmission into NEUTRAL.
  4. Set the parking brake.
  5. Observe Commanded Mode Indicator States on the scan tool, while selecting each of the mode positions.
Does the state change with the selection of any of the mode positions?		 Go to Step 5  Go to Step 3 
3 
  1. Use a scan tool in order to command through the modes of the transfer case shift control switch.
  2. With a scan tool, command through all Commanded Mode Indicator states.
Does the Mode Indicator state change?		 Go to Step 4  Go to Step 5 
4 Replace the transfer case shift control switch. Refer to Transfer Case Shift Control Switch Replacement (GMC, Buick)  or Transfer Case Shift Control Switch Replacement (Chevrolet)  .
Did you complete the repair?		 Go to Step 6  -
5
IMPORTANT: After transfer case shift control module replacement and reprogramming, ensure all doors are closed and the key is out of the ignition, then open and close the doors again and wait 2 minutes to avoid incomplete programming or false communication DTCs.
Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming  .Did you complete the repair?		 Go to Step 6  -
6
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle in order to determine if the symptom has been corrected.
Is the symptom still present?		 Go to Step 2  System OK
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