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Home >> Chevrolet >> 2004 >> Avalanche 2500 >> Repair and Diagnosis >> External Pages >> Different car >> Section 411 (Transfer Case - BW 4482-Nr4) >> Diagnostic Information and Procedures >> Diagnostic System Check - Transfer Case >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Yukon XL and 2004 GMC Yukon. 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:  Lack of communication may be due to a partial malfunction of the Class 2 serial data circuit or due to a total malfunction of the Class 2 serial data circuit. The specified procedure will determine the particular condition.
  2. 3:  A fuse failure will cause no communication this step has you check for this condition.
  3. 4:  This step determines if the fuse blows when the ignition is turned on.
  4. 5:  This step determines if there is a short to ground in the battery positive circuit causing the fuse to blow.
  5. 6:  This step refers to the table for DTC C0306 for further diagnosis if a transfer case mode change is causing the fuse to blow.
  6. 7:  The presence of DTCs indicates that the transfer case shift control module has detected a fault. Go to symptoms for other concerns.
  7. 8:  The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.
  8. 9:  Vehicle speed is provided to the transfer case shift control module via Class 2 and can effect the setting of DTC C0300. Perform the diagnostics for powertrain DTCs P0502 and P0503 first.
Diagnostic System Check - Transfer Case

Step Action Yes No
1 Install a scan tool.
Does the scan tool power up?		 Go to Step 2  Go to Scan Tool Does Not Power Up in Data Link Communications
2 
  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with the transfer case shift control module.
Does the scan tool communicate with the transfer case shift control module?		 Go to Step 7  Go to Step 3 
3 
  1. Turn off the ignition.
  2. Check the underhood TREC fuse.
Did the TREC fuse blow?		 Go to Step 4  Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications
4 
  1. Replace the TREC fuse.
  2. Turn on the ignition.
Does the TREC fuse blow?		 Go to Step 5  Go to Step 6 
5  Check the battery positive circuit for a short to ground.
Was the condition found and corrected?		 Go to Step 2  Go to Transfer Case Shift Control Module Replacement 
6 
  1. Start the Engine
  2. Attempt to shift the transfer case to different modes.
  3. Check the underhood TREC fuse.
Did the TREC fuse blow?		 Go to DTC C0306  Go to Step 2 
7  Select the transfer case shift control module display DTCs function on the scan tool.
Does the scan tool display any DTCs?		 Go to Step 8  Go to Symptoms - Transfer Case 
8  Does the scan tool display any DTCs which begin with a "U"? Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications Go to Step 9 
9  Does the scan tool display DTC P0502 or P0503? Go to Applicable Powertrain OBD Diagnostic System Check Go to Diagnostic Trouble Code (DTC) List 
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