GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Avalanche - 4WD 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Transfer Case Shift Control Switch Indicator Inoperative - One or More

Circuit Description

The indicator lamps circuit consists of the following 3 individual lamps contained inside the mode switch assembly:

    • All wheel drive (AWD)
    • 4LO
    • Neutral

The following lamps are contained inside their respective mode button.

    • AWD
    • 4LO

When the ignition in ON, the transfer case shift control module illuminates the indicator lamp that corresponds to the current transfer case gear position by providing a ground through a current limiting driver.

The transfer case shift control module flashes each indicator lamp after a shift has been requested and will continue to flash until the transfer case shift control module can complete the shift.

A solid state circuit located inside the switch supplies ignition voltage to the lamps. The solid state circuit also receives voltage whenever the headlamp switch is in the park lamp or headlamp position. When the solid state circuit receives voltage from the headlamp switch it will reduce the voltage that it supplies to the indicator lamps, dimming the lamps when the headlamps are ON.

Test Description

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

  1. This step determines if the module can command the indicators ON.

    2.

  2. This step determines if the indicator or wiring is at fault.

    3.

  3. This step tests the lamp feed circuit for an open or high resistance.

    4.

  4. This step tests the LED dimming circuit for an open or short to ground.

Step

Action

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?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Turn ON the ignition, with the engine OFF.
  2. Install a scan tool.
  3. Use the scan tool in order to command all the indicator lamps ON.

Do all the lamps turn ON?

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

Go to Step 3

3

Important: Do not damage a connector or circuit when back probing.

  1. Access the back of the mode switch.
  2. Using a fused jumper back probe the effected indicator control circuit to ground.

Does the effected lamp turn ON?

Go to Step 4

Go to Step 5

4

Test the effected indicator control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Was the condition found and corrected?

Go to Step 8

Go to Step 7

5

Test the LED dimming 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 8

Go to Step 6

6

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

Is the repair complete?

Go to Step 8

--

7

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

Is the repair complete?

Go to Step 8

--

8
  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