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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Yukon XL Denali 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Transfer Case Shift Control Switch Inoperative

Circuit Description

The range/mode switch circuit consists of the following 5 switches:

    • 2HI
    • 4HI
    • 4LO
    • AUTO 4WD
    • Neutral

The transfer case shift control module supplies a regulated 5 volts, DC to the switch through the 5 volt regulator circuit. The current travel through the resistor of the currently active switch. The switch then returns current to the transfer case shift control module through the switch signal circuit.

The transfer case shift control module constantly monitors this signal voltage to determine the condition of the mode switch circuit.

When each switch is depressed, the switch completes a circuit through the respective resistor. The transfer case shift control module continuously monitors the switch input to determine which of the following buttons were selected by the driver:

    • 2HI
    • 4HI
    • 4LO
    • AUTO 4WD

Test Description

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

  1. This step tests the functionality of the mode switch.

    2.

  2. This step tests the modules ability to operate the transfer case modes.

Step

Action

Yes

No

Schematic Reference: Transfer Case Control Schematics

Connector End View Reference: Transfer Case Control Connector End Views

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 - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Start the engine.
  3. Place the transmission into Neutral.
  4. Set the park brake.
  5. Use a scan tool in order to observe the Commanded Mode Indicator parameter while selecting each of the Mode positions.

Does the state change with the selection of any of the mode positions?

Go to Step 4

Go to Step 3

3

Replace the transfer case shift control switch. Refer to Transfer Case Shift Control Switch Replacement .

Did you complete the repair?

Go to Step 5

--

4

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.

  1. Replace the transfer case shift control module. Refer to Control Module References for replacement, setup, and programming.
  2. Perform the Clutch Reset Procedure. Refer to Transfer Case High/Low Clutch Reset .

Did you complete the repair?

Go to Step 5

--

5
  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