GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2006 🢒 Colorado Pickup - 4WD 🢒 Driveline/Axle 🢒 Transfer Case - Isuzu T150 🢒 Accessory Switch Transfer Case Mode Indicator Always On - Two 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

When the ignition in 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 lamp after a shift has been requested, and continues 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 when the headlamp switch is in the parklamp or headlamp position. When the solid state circuit receives voltage from the headlamp switch, the switch reduces the voltage supplied 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 tests the transfer case electrical control of the lamp circuits.

    2.

  2. This step helps determine if there is a short to ground in the suspect indicator control circuits.

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 indicator lamps OFF.

Do all the lamps go OFF?

Go to Step 5

Go to Step 3

3

  1. Drive the vehicle to determine the transfer case mode.
  2. Use this information to determine which indicator control circuits are at fault.
  3. Disconnect the accessory switch.
  4. Test the suspect indicator control circuits for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs .

Did you find and correct the condition?

Go to Step 6

Go to Step 4

4

Replace the accessory switch. Refer to Accessory 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 to determine if the symptom has been corrected.

Is the symptom still present?

Go to Step 2

System OK