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For 1990-2009 cars only
Makes 🢒 HUMMER 🢒 2008 🢒 H2 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Transfer Case Shift Control Switch Inoperative

Circuit Description

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

    • 4HI
    • 4HI Lock
    • 4LO Lock
    • Differential Lock
    • Neutral

The transfer case shift control module supplies a regulated 5 volts, DC, to the switch through the 5-volt regulator circuit. The current travels through the resistor of the currently active switch. The switch then returns the 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 will complete a circuit through the respective resistor. The transfer case shift control module continuously monitors the switch input to determine which of the following buttons is selected by the driver:

    • 4HI
    • 4HI Lock
    • 4LO Lock
    • Differential Lock

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: Component Connector End Views

1

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. Observe the Mode Switch Selected parameter on the scan tool while selecting each of the mode positions on the switch.

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

Go to Step 5

Go to Step 3

3

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

Did you find and correct the condition?

Go to Step 6

Go to Step 4

4

Replace the mode selection switch. Refer to Transfer Case Shift Control Switch Replacement .

Did you complete the repair?

Go to Step 6

--

5

Replace the transfer case shift control module. Refer to Control Module References for replacement, setup and programming.

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