GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 HUMMER 🢒 2003 🢒 H2 🢒 Driveline/Axle 🢒 Transfer Case - BW 4484 🢒 Electronic Rear Differential Lock Will Not Disengage

Circuit Description

The rear differential control circuit consists of a actuator (coil) which engages and disengages the rear axle differential lock. The rear differential actuator consists of a coil assembly, and a locking assembly with springs and pins to lock the rear differential, all within the rear differential assembly.

The rear axle differential lock actuator consists of the following circuits:

    • The rear differential lock control circuit, which is connected to the transfer case shift control module and supplies battery voltage.
    • The rear differential lock return (ground) circuit, which is also connected to the transfer case shift control module.

Whenever the rear differential lock has been requested the transfer case shift control module provides battery voltage through the rear differential lock control circuit, and provides ground through the rear differential lock return circuit through a current limiting driver.

Whenever a rear differential lock is requested the transfer case must be in 4LO and the vehicle speed must be below 5 km/h (3 mph) for the request to be accepted. The rear differential lock will remain locked up to 32 km/h (20 mph) after which the rear differential lock will disengage.

Test Description

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

  1. This step determines if the differential lock is engaged due to an electrical condition or a mechanical condition.

    2.

  2. This step determines if the differential lock high control circuit is shorted to power and if the differential low reference circuit is shorted to ground.

    3.

  3. This step indicates the transfer case shift control module needs replaced.

    4.

  4. This step checks for the possibility of the rear differential mechanically binding causing it to stay on.

Step

Action

Yes

No

Schematic Reference: Differential Lock Schematics

Connector End View Reference: Rear Axle Connector End Views

1

Did you perform the Diagnostic System Check-Transfer Case?

Go to Step 2

Go to Diagnostic System Check - Transfer Case in Transfer Case - BW4484

2

Disconnect the rear differential lock harness from the rear differential lock coil pigtail at the rear differential, and verify the fault is present. Refer to Locking Differential Diagnosis .

Does the system operate normally?

Go to Step 3

Go to Step 5

3

Check the rear differential lock high control circuit for a short to power and the differential lock low reference for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Was the condition found and corrected?

Go to Step 6

Go to Step 4

4

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

Was the repair completed?

Go to Step 6

--

5

Replace the electronic locking differential locking mechanism and/or side gear. Refer to Locking Differential Disassemble and Locking Differential Assemble .

Was the condition repaired?

Go to Step 6

--

6
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for allowing the symptom to re-occur.

Does the symptom re-occur?

Go to Step 1

System OK