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Test Description

WARNING: This page is about a different car, the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 Chevrolet Tahoe, 2002 Chevrolet Suburban, and 2002 Chevrolet Avalanche. 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:  Tests for proper operation of the transfer case mode select switch.
  2. 3:  Tests for proper voltage supply to the transfer case mode select switch.
  3. 4:  Tests the transfer case mode select switch for proper resistance values in all switch states.
  4. 5:  Tests the switch signal circuit for a short to voltage.
  5. 6:  Tests the switch signal circuit for an open or short to ground.
  6. 7:  Tests the switch signal circuit for a short to the 8 V Reg circuit.
  7. 8:  Determines whether the 8 V Reg circuit is greater than or less than the specified voltage.
  8. 9:  Tests the 8 V Reg circuit for a short to voltage.
  9. 10:  Tests the 8 V Reg circuit for an open or short to ground.
DTC B2725

Step Action Values Yes No
Schematic Reference:  Transfer Case Control Schematics  
1 Was the Transfer Case Diagnostic System Check performed? - Go to Step 2  Go to Diagnostic System Check - Transfer Case 
2 
IMPORTANT: Neutral Range will only be obtained by pressing and holding both the 2 HI and the 4 LO buttons simultaneously for 10 seconds. Refer to Circuit Description.
  1. Install a Scan Tool.
  2. Start the engine.
  3. Place the transmission into NEUTRAL (or clutch pedal depressed on the manual transmission applications).
  4. Set the park brake.
  5. With a scan tool, observe the Mode Switch Selected data parameter in the Transfer Case data list.
  6. Depress and hold each of the Mode buttons while viewing the mode switch selected parameter on the scan tool.
Does the scan tool indicate that the Mode Switch Selected data parameter is indicating the correct state?		 - Go to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems Go to Step 3 
3 
  1. Turn the ignition to OFF.
  2. Disconnect the mode switch.
  3. Turn the ignition to ON, with the engine OFF.
  4. Measure the voltage from 8 V Reg Circuit to a good ground.
Does the voltage measure within the specified range?		 7-9 V Go to Step 4  Go to Step 8 
4 
  1. Connect a DMM between the Mode Switch Signal Circuit and the 8 V Reg circuit at the switch.
  2. Measure the resistance through the selector mode switch while depressing the mode buttons and comparing the values.
Does the DMM indicate all resistance values within the specified ranges?		 Normal 8.63- 9.54 K Ω Auto 4 WD 61.7- 68.1 Ω 4 HI 656-670 Ω 2 HI 1.50-1.53 K Ω 4 LO 2.32-2.37 K Ω Neutral 1.015 - 1.035 KΩ Go to Step 5  Go to Step 11 
5 
  1. Turn the ignition OFF.
  2. Disconnect the transfer case shift control module.
  3. Turn the ignition ON, with the engine OFF.
  4. Test the switch signal circuit for a short to voltage. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Was the condition found and corrected?		 - Go to Step 13  Go to Step 6 
6  Test the switch signal circuit for an open or short to ground. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Was the condition found and corrected?		 - Go to Step 13  Go to Step 7 
7  Test the switch signal circuit for a short to the 8 V Reg circuit. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Was the condition found and corrected?		 - Go to Step 13  Go to Step 12 
8  Was the voltage measured in Step 3 greater than the specified value? 9 V Go to Step 9  Go to Step 10 
9 
  1. Turn OFF the ignition.
  2. Disconnect the transfer case shift control module.
  3. Turn ON the ignition, with the engine OFF.
  4. Test the 8 V Reg circuit for a short to voltage. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Was the condition found and corrected?		 - Go to Step 13  Go to Step 12 
10 
  1. Turn OFF the ignition.
  2. Disconnect the transfer case shift control module.
  3. Turn ON the ignition, with the engine OFF.
  4. Test the 8 V Reg circuit for an open or short to ground. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Was the condition found and corrected?		 - Go to Step 13  Go to Step 12 
11 Replace the mode switch. Refer to Transfer Case Shift Control Switch Replacement .
Is the repair complete?		 - Go to Step 13  -
12 Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement .
Is the repair complete?		 - Go to Step 13  -
13
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?		 - Go to Step 2  System OK
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