GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 Canyon Pickup - 4WD 🢒 Driveline/Axle 🢒 Transfer Case - Isuzu T150 🢒 Accessory Switch Transfer Case Mode Indicator Flashes in 4WD High,4WD Low, and 2WD Modes

Circuit Description

The Isuzu T150 transfer case contains a neutral switch, which is supplied battery voltage by the transfer case shift control module. When the transfer case mode selection is in neutral the neutral switch provides a path to ground pulling the neutral signal circuit low. This assists the transfer case shift control module in determining the present mode. A fault in the 2WD/4WD signal circuit, or the neutral switch signal circuit will cause the neutral mode indicator to flash. A fault in the front axle actuator or the corresponding front axle actuator circuits can also cause the neutral mode indicator to flash.

Diagnostic Aids
    • Check the inline connector C105 for proper connection, bent pins, damage, or corrosion. Refer to Harness Routing Views in Wiring Systems.
    • 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 in Wiring Systems.
    • Check for water leaks at doors and bulkhead areas. Refer to Waterleak Test Preparation .
    • Check the 2WD/4WD and Neutral switch for proper connection, bent pins, or damaged terminals. Refer to Transfer Case Control Component Views .

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step determines if the neutral switch is causing the symptom.

    2.

  2. This step determines if an open neutral signal circuit is causing the symptom.

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 - Transfer Case?

Go to Step 2

Go to Diagnostic System Check - Transfer Case

2

  1. Set the parking brake.
  2. Turn the ignition ON with the engine OFF.
  3. Place the transmission into neutral.
  4. Shift the vehicle to 2WD, 4WD High, and 4WD Low.

Do each of the mode indicators flash in each of the three modes?

Go to Step 3

Go to Symptoms - Transfer Case

3

  1. Lift the vehicle on a hoist. Refer to Lifting and Jacking the Vehicle in General Information.
  2. Disconnect the transfer case neutral switch.
  3. Shift the transfer case into 2WD, 4WD High, and 4WD Low.

Does the indicator continue to flash in all three modes?

Go to Step 4

Go to Step 5

4

  1. Disconnect connector C2 at the transfer case shift control module.
  2. Test the neutral signal circuit for a short to ground. Refer to Testing for Short to Ground in Wiring Systems.

Did you find and correct the condition?

Go to Step 5

Go to Step 6

5

Replace the transfer case neutral switch. Refer to Transfer Case Neutral Switch Replacement .

Did you complete the repair?

Go to Step 7

--

6

Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement

Did you complete the repair?

Go to Step 7

--

7

Operate the vehicle in order to determine if the symptom has been corrected.

Is the symptom still present?

Go to Step 1

System OK