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, then Returns to Previous Mode

Circuit Description

The transfer case motor is a bi-directional, permanent magnet, D.C. motor. When energized, through motor control A or motor control B, the ground is provided by the opposing motor control circuit and then grounded through the transfer case shift control module ground circuit. The motor, through a series of gears, rotates a shaft which moves the mode and range forks to shift the transfer case between the following ranges:

    • 2HI
    • 4HI
    • 4Low
    • N

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 .

Test Description

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

  1. This step checks the TCCM fuse for an open.

    2.

  2. This step engages the motor control A and B circuits.

    3.

  3. This step rechecks the TCCM fuse for an open.

    4.

  4. This step determines if a short to ground in the motor control A or motor control B circuit is causing the TCCM fuse to open.

    5.

  5. This step checks the motor winding for an internal short to ground.

    6.

  6. This step checks the motor windings for high resistance.

    7.

  7. This step tests the motor control A circuit for an open, or high resistance.

    8.

  8. This step tests the motor control B circuit for an open, or high resistance.

    9.

  9. This step tests the ignition 1 and battery positive circuits going to the transfer case shift control module for an open or high resistance.

    10.

  10. This step tests the ground circuits going to the transfer case shift control module for an open or high resistance.

    11.

  11. This step tests for motor control A and motor control B circuits being shorted together.

Step

Action

Value(s)

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

Check the TCCM fuse in the underhood fuse block and replace as necessary. Refer to Circuit Protection - Fuses in Wiring Systems.

Did you complete the repair?

--

Go to Step 3

--

3

With a scan tool using special functions, engage and disengage motor control A.

Does the motor move in both directions?

--

Go to DTC C0327

Go to Step 4

4

Check the TCCM fuse for being open.

Is the TCCM fuse open?

--

Go to Step 5

Go to Step 7

5

  1. Disconnect connectors C1 and C2 from the transfer case shift control module.
  2. Check the motor control A and motor control B circuits for a short to ground. Refer to Testing for Short to Ground in Wiring Systems.

--

Go to Step 17

Go to Step 6

6

  1. Engage the parking brake.
  2. Turn the ignition OFF and raise the vehicle on a hoist. Refer to Lifting and Jacking the Vehicle in General Information.
  3. Disconnect the encoder motor connector at the transfer case.
  4. With a DMM check the motor windings for an internal short to ground by probing the motor A control or motor B control pins on the encoder motor and taking the other lead to ground.

Does the DMM indicate a short to ground?

--

Go to Step 15

Go to Step 7

7

With a DMM check the resistance of the motor windings by probing the motor A control and motor B control pins on the encoder motor.

Does the DMM indicate a reading within the specified range?

2-100 ohms

Go to Step 8

Go to Step 15

8

  1. Disconnect the transfer case control module.
  2. With a DMM test the motor control A circuit for an open, or high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 17

Go to Step 9

9

With a DMM test the motor control B circuit for an open, or high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 17

Go to Step 10

10

With a DMM test the battery positive voltage and Ignition 1 voltage circuits, going to the transfer case shift control module, for an open or high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 17

Go to Step 11

11

With a DMM test the transfer case shift control module ground circuits for an open or high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 17

Go to Step 12

12

With a DMM, test motor control A and motor control B circuits for being shorted together.

Did you find and correct the condition?

--

Go to Step 17

Go to Step 13

13
  1. Remove the encoder motor.
  2. Inspect the shift detent lever shaft for a binding condition. Refer to Transfer Case Encoder Motor Replacement .

Did the shift detent lever shaft bind?

--

Go to Step 14

Go to Step 16

14

Remove the transfer case for disassembly and repair. Refer to Transfer Case Disassemble in Unit Repair.

Did you complete the repair?

--

Go to Step 17

--

15

Replace the encoder motor. Refer to Transfer Case Encoder Motor Replacement .

Did you complete the repair?

--

Go to Step 17

--

16

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

Did you complete the repair?

--

Go to Step 17

--

17
  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 1

System OK