GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 TopKick C-Series (Conventional) C6/C7/C8 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Transfer Case Shift Control Switch Inoperative

Circuit Description

The range/mode switch circuit consists of the following 4 switches:

    • 2HI
    • 4HI
    • 4LO
    • 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

Test Description

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

  1. This step tests for proper operation of the transfer case mode select switch.

    2.

  2. This step tests the mode switch for proper resistance values in all mode switch states.

    3.

  3. This step tests the switch signal wire for a short to ground, short to voltage, or high resistance

Step

Action

Values

Yes

No

Schematic Reference: Transfer Case Control Schematics

Connector End View Reference: Transfer Case Control Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Install a scan tool.
  2. Start the engine.
  3. Set the parking brake.
  4. Place the transmission into Neutral.
  5. With a scan tool, observe the Mode Switch Selected parameter.
  6. Select each of the modes.

Does the scan tool indicate that the modes are in the correct state while pressing the mode buttons?

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Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3
  1. With the switch disconnected, connect a DMM between the mode switch signal circuit and the 5-volt reference circuit at the switch.
  2. Measure the resistance through the mode switch while pressing and holding each of the mode buttons and comparing values.

Does the DMM indicate all resistance values within the specified ranges?

4 HI: 1,042-1,107 ohms

2 HI: 230-245 ohms

Neutral: 4,467-4,743 ohms

4 LO: 2,039-2,165 ohms

Go to Step 4

Go to Step 5

4

Test the switch signal and 5-volt reference circuits for a short to voltage, short to ground or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 7

Go to Step 6

5

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

Did you complete the repair?

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Go to Step 7

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6

Replace the transfer case shift control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the repair?

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Go to Step 7

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7

  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?

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Go to Step 2

System OK