Hummer H2. Manual - part 888

LOCKING DIFFERENTIAL DISASSEMBLED VIEWS 

Connector Part Information

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15326801  

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2-Way F GT 150 Series (BK)  

Pin

Wire Color

Circuit No.

Function

A

BK

1725

Rear Differential Lock - Low Reference

B

L-GN

2659

Rear Differential Lock - High - Control

 

2004 Hummer H2 

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

  

Fig. 3: Locking Differential Component Views 
Courtesy of GENERAL MOTORS CORP. 

Callouts For Fig. 3 

Callout

Component Name

1

Differential Bearing Retainer Ring

2

Differential Bearing Race

3

Differential Bearing Assembly

4

Locking Differential Coil Assembly

5

Locking Differential Coil Plate

6

Locking Differential Ball Bearing Plate - Outboard

7

Locking Differential Ball Bearing Assembly

8

Locking Differential Ball Bearing Plate - Inboard

9

Locking Differential Clutch Spring

10

Locking Differential Clutch Spring Retainer

11

Differential Carrier Lock Pin

12

Differential Side Gear Thrust Washer

13

Locking Differential Side Gear

14

Pinion Thrust Washer

15

Differential Pinion Gear

16

Differential Side Gear

 

2004 Hummer H2 

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

  

DIAGNOSTIC INFORMATION AND PROCEDURES 

DIAGNOSTIC STARTING POINT - LOCKING/LIMITED SLIP REAR AXLE 

Begin the system diagnosis by reviewing the system Description and Operation. Reviewing the Description and 
Operation information will help you determine the correct symptom diagnostic procedure when a malfunction 
exist. Reviewing the Description and Operation information will also help you determine if the condition 
described by the customer is normal operation. Refer to Symptoms - Locking/Limited Slip Rear Axle in order 
to identify the correct procedure for diagnosing the system and where the procedure is located. 

DTC C0388 

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: 

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

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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 4 LO 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. 

This DTC detects a short to ground, short-to-voltage, or an open circuit. 

Conditions for Running the DTC 

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The ignition is ON.  

17

Differential Side Gear Thrust Washer

18

Differential Pinion Gear

19

Pinion Thrust Washer

20

Differential Pinion Shaft Lock Screw

21

Electric Locking Differential Case Assembly

22

Differential Pinion Gear Shaft

 

2004 Hummer H2 

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

  

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System voltage is 9-18 volts.  

Conditions for Setting the DTC 

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The transfer case shift control module monitors the state of the rear axle differential lock actuator. The 
transfer case shift control module reads the rear differential lock control, and the rear differential lock 
return circuits for a high and low voltage. The DTC will set if these circuits are high when a low voltage 
is expected or when the circuits are low when a high voltage is expected.  

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The DTC will set if this circuit is high when a low voltage is present or when the circuit is low when a 
high voltage is present.  

Action Taken When the DTC Sets 

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All rear differential lock requests will be disabled. Transfer case mode shifts will not be affected  

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SERVICE 4WD indicator will be latched on for the remainder of the current ignition cycle.  

Conditions for Clearing the DTC 

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The Transfer case shift control module will clear the DTC if the condition for setting the DTC is not 
currently present.  

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A history DTC will clear after 33 consecutive ignition cycles without a fault present.  

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History DTCs can be cleared using a scan tool.  

Test Description 

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

2: This step determines of the coil has excessive resistance or if the windings are shorted together.  

3: This step determines if the coil or pigtail is shorted to ground.  

4: This step determines if either the differential lock control or differential lock return circuits are shorted 
to ground.  

5: This step determines if the differential lock control and differential lock return circuits are shorted 
together.  

6: This step tests for an open or high resistance in both the return and control circuits.  

7: This step refers to transfer case shift control module replacement.  

8: This step refers to encoder motor replacement.  

DTC C0388 

Step

Action

Value 

(s)

Yes

No

Schematic Reference: Transfer Case Control Schematics in Transfer Case - BW 4484 
Connector End View Reference: Rear Axle Connector End Views

Did you perform the Diagnostic System Check - Transfer 
Case?

Go to Diagnostic 

System Check - 

 

2004 Hummer H2 

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