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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Canyon Pickup - 4WD 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Accessory Switch Transfer Case Mode Indicator Inoperative - One or More

Circuit Description

The indicator lamps circuit consist of the following 4 individual lamps contained inside the accessory switch assembly:

    • 2HI
    • 4HI
    • 4LO
    • Neutral

The following lamps are contained inside the respective range button for each lamp:

    • 2HI
    • 4HI
    • 4LO

Each time the ignition is cycled, all 4 mode indicators light simultaneously as an indicator check, to ensure proper operation of the indicators. When the ignition is ON, the transfer case shift control module illuminates the indicator 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 after a shift has been requested, and continues to flash until the transfer case shift control module completes the shift.

A solid state circuit located inside the switch supplies ignition voltage to the lamps. The solid state circuit also receives voltage when the headlamp switch is in the parklamp or headlamp position. When the solid state circuit receives voltage from the headlamp switch, the circuit reduces the voltage that is supplied to the indicator lamps, dimming the lamps when the headlamps are ON.

Diagnostic Aids
    • Check the inline connector C200 for proper connection, bent pins, damage, or corrosion. Refer to Harness Routing Views and Delphi Connectors .
    • Check the transfer case shift control module connectors C1 and C2 for proper connection and bent or corroded pins or terminals. Refer to Repairing Connector Terminals .
    • Check for water leaks at doors and bulkhead areas. Refer to Waterleak Test Preparation .

Test Description

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

  1. This step tests the transfer case electrical control of the lamp circuits.

    2.

  2. This step helps determine module failures.

    3.

  3. This step tests the affected indicator control circuit for an open or high resistance.

    4.

  4. This step tests the LED dimming supply 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

2

  1. Turn the ignition ON, with the engine OFF.
  2. Install a scan tool.
  3. Using the scan tool, command all the indicators ON.

Do all the indicators illuminate?

Go to Step 7

Go to Step 3

3

  1. Access the back of the accessory switch.
  2. Backprobe the indicator control circuit of the affected indicator to ground.

Does the affected indicator go ON?

Go to Step 7

Go to Step 4

4

Test the affected indicator control circuit for an open or high resistance. Refer to Testing for Continuity and Wiring Repairs .

Did you find and correct the condition?

Go to Step 8

Go to Step 5

5

Test the LED dimming supply circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 8

Go to Step 6

6

Replace the accessory switch. Refer to Accessory Switch Replacement .

Did you complete the repair?

Go to Step 8

--

7

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 8

--

8
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle to determine if the symptom has been corrected.

Is the symptom still present?

Go to Step 2

System OK