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 Neutral Mode

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 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 front axle actuator is causing the symptom.

    2.

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

    3.

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

    4.

  4. This step determines if a shorted to ground 2WD/4WD switch 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. Shift the transmission into neutral.
  4. Shift the transfer case into neutral.
  5. Raise the vehicle on a hoist. Refer to Lifting and Jacking the Vehicle in General Information.
  6. With the vehicle on the hoist spin the front tires.

Does the front propshaft turn when the front tires are spun?

Go to Front Axle Will Not Disengage

Go to Step 3

3
  1. Raise the vehicle on a hoist. Refer to Lifting and Jacking the Vehicle in General Information.
  2. Disconnect the transfer case neutral switch and remove the switch.
  3. Turn the ignition ON.
  4. Connect the transfer case neutral switch and depress the plunger.

Does the neutral indicator light continue to flash?

Go to Step 4

Go to Transfer Case Assembly Replacement

4

With a fused jumper wire short the neutral signal circuit to the ground pin on the switch connector. Refer to Using Fused Jumper Wires and Wiring Repairs in Wiring Systems.

Does the neutral mode indicator continue to flash?

Go to Step 5

Go to Step 7

5

Test the neutral signal and ground circuits for an open. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 9

Go to Step 6

6

Disconnect the 2WD/4WD switch and test the 2WD/4WD switch signal circuit for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 9

Go to Step 8

7

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

Did you complete the repair?

Go to Step 9

--

8

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

Did you complete the repair

Go to Step 9

--

9

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

Is the symptom still present?

Go to Step 1

System OK