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