Hummer H2. Manual — part 890

5

and the transfer case shift control module.
Refer to Circuit Testing and Wiring Repairs
in Wiring Systems.
Was the condition found and corrected?

-

Go to Step 13

Go to Step 6

6

1. Disconnect the rear differential lock

harness from the rear differential lock
coil pigtail.

2. With a DMM, measure the resistance of

the rear differential lock coil and pigtail
by probing the rear differential lock
return and the rear differential lock
control circuits.

Was the resistance reading within the
specified values?

2.2-4.3

ohm

Go to Step 7

Go to Step 11

7

With the connector still disconnected, with a
DMM, probe the return then the control
circuits and check for resistance to ground.
Did the DMM indicate a short to ground?

-

Go to Step 11

Go to Step 8

8

1. Disconnect the C1 from the transfer

case shift control module.

2. Disconnect the rear differential lock

harness from the rear differential coil
pigtail.

3. Turn the ignition ON.

4. With a DMM, check for a short to

power or short to ground on the
differential lock control and differential
lock return circuits. Refer to Circuit
Testing and Wiring Repairs in Wiring
Systems.

Was the condition found and corrected?

-

Go to Step 13

Go to Step 9

9

Check the differential lock control and
differential lock return circuits for an open or
high resistance. Refer to Circuit Testing and
Wiring Repairs in Wiring Systems.
Was the condition found and corrected?

-

Go to Step 13

Go to Step 10

10

Replace the transfer case shift control module.
Refer to Transfer Case Shift Control
Module Replacement in Transfer Case -
BW4484.
Was the repair completed?

-

Go to Step 13

-

Replace the electronic locking differential

2004 Hummer H2

2004 DRIVELINE/AXLE Drive Axle - Locking/Limited Slip - Hummer H2

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:

z

The rear differential lock control circuit, which is connected to the transfer case shift control module and
supplies battery voltage.

z

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.

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

11

locking mechanism and/or side gear. Refer to
Locking Differential Disassemble and
Locking Differential Assemble .
Was the repair completed?

-

Go to Step 13

-

12

Replace the transfer case shift control switch.
Refer to Transfer Case Shift Control Switch
Replacement in Transfer Case - BW4484.
Was the repair completed?

-

Go to Step 13

-

13

1. Use the scan tool in order to clear the

DTCs.

2. Operate the vehicle within the

Conditions for allowing the symptom to
occur.

Does the symptom occur?

-

Go to Step 1

System OK

2004 Hummer H2

2004 DRIVELINE/AXLE Drive Axle - Locking/Limited Slip - Hummer H2

3: 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.

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

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

Electronic Rear Differential Lock Will Not Disengage

REPAIR INSTRUCTIONS

LOCKING DIFFERENTIAL COIL ASSEMBLY REPLACEMENT

Removal Procedure

1. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.

2. Remove the differential assembly. Refer to Differential Replacement in Rear Drive Axle.

3. Remove the differential side bearing. Refer to Differential Side Bearings Replacement in Rear Drive

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 in
Transfer Case - BW4484.
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

2004 Hummer H2

2004 DRIVELINE/AXLE Drive Axle - Locking/Limited Slip - Hummer H2

Axle.

Fig. 4: Differential Bearing Retainer
Courtesy of GENERAL MOTORS CORP.

4. Remove the differential bearing retainer by performing the following steps:

1. With the aid of an assistant, push the differential bearing race down towards the differential case in

IMPORTANT: The differential bearing race must be compressed in order to remove the

differential bearing retainer.

2004 Hummer H2

2004 DRIVELINE/AXLE Drive Axle - Locking/Limited Slip - Hummer H2