Hummer H2. Manual - part 2655

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

1. Set the parking brake.  

2. Raise the vehicle on a hoist.  

3. Disconnect the connector at the transfer case.  

4. Turn the ignition ON, with the engine OFF.  

5. Install a scan tool.  

6. Monitor the encoder channels P, B, A, and C on 

the scan tool.  

Do any of the encoder channels indicate OFF?

-

Go to 

Step 3

Go to Step 4

3

Test the encoder channel circuit that is indicating OFF 
on the scan tool for a short to ground. Refer to Circuit 
Testing and Wiring Repairs in Wiring Systems. 
Did you find and correct the condition?

-

Go to 

Step 9

Go to Step 8

4

With the ignition in the OFF position, test the encoder 
low reference circuit for a short to ground. Refer to 
Circuit Testing and Wiring Repairs in Wiring 
Systems. 
Did you find and correct the condition?

-

Go to 

Step 9

Go to Step 5

5

1. Turn the ignition ON with the engine OFF.  

2. With the transfer case connector still 

disconnected, use the scan tool to clear DTCs.  

Does DTC C0329 reset?

-

Go to 

Step 8

Go to Step 6

6

1. Turn the ignition OFF.  

2. Connect the transfer case connector.  

3. Turn the ignition ON, with the engine OFF.  

4. With the transfer case shift control switch, 

command the transfer case through all of the 
modes.  

5. Using a scan tool, check DTCs.  

Does DTC C0329 set?

-

Go to 

Step 7

Go to Testing for 

Electrical Intermittents 

in Wiring Systems

7

Replace the encoder motor. Refer to Transfer Case 
Motor/Encoder Replacement . 
Did you complete the repair?

-

Go to 

Step 9

-

8

Replace the transfer case shift control module. Refer to 
Transfer Case Shift Control Module Replacement . 
Did you complete the repair?

-

Go to 

Step 9

-

 

2004 Hummer H2 

2004 DRIVELINE/AXLE Transfer Case - BW 4484 - Hummer H2

  

DTC C0359 

Circuit Description 

The 4WD low signal circuit is used to notify the powertrain control module (PCM) that the vehicle is in 4WD 
low range. The PCM supplies 12 volts to this circuit. The transfer case shift control module grounds this circuit 
when the vehicle is in 4WD low range. 

This DTC detects a short to ground, short to voltage, or an open in the 4WD low signal circuit. 

Conditions for Running the DTC 

z

The ignition is ON.  

z

The system voltage is 9-18 volts.  

Conditions for Setting the DTC 

z

After the transfer case shift control module grounds the output, the 4WD Low signal circuit, and reads 
back a high voltage, the DTC is set. The system will not attempt setting the DTC again during that 
ignition cycle.  

z

The transfer case shift control module reads back a high voltage when a low voltage is expected on the 
4WD low signal circuit.  

Action Taken When the DTC Sets 

z

Transmission shift points may be affected.  

z

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

Conditions for Clearing the DTC 

z

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

z

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

z

History DTCs can be cleared using a scan tool.  

Test Description 

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

9

1. Use the scan tool in order to clear the DTCs.  

2. Operate the vehicle within the Conditions for 

Running the DTC as specified in the supporting 
text.  

Does the DTC set?

-

Go to 

Step 1

System OK

 

2004 Hummer H2 

2004 DRIVELINE/AXLE Transfer Case - BW 4484 - Hummer H2

  

2: This step tests for proper reference voltage to the transfer case shift control module on the 4WD low 
signal circuit.  

3: This step tests the 4WD low signal circuit for a short to voltage.  

4: This step tests the 4WD low signal circuit for an open or high resistance.  

5: This step repairs the 4WD low signal circuit for a short to voltage.  

DTC C0359 

Step

Action

Values

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

1. Turn the ignition OFF.  

2. Disconnect the transfer case shift control module.  

3. Turn the ignition ON, with the engine OFF.  

4. Measure the voltage between the 4WD low signal 

circuit harness and ground.  

Is the voltage reading within the specified values?

10-13.5 

V

Go to 

Step 3

Go to Step 4

3

1. Disconnect the powertrain control module (PCM).  

2. Measure the voltage between the 4WD low signal 

circuit harness and ground.  

Is the voltage reading within the specified value?

0 V

Go to 

Step 7

Go to Step 5

4

Test the 4WD low signal circuit for an open, high 
resistance, or short to ground. Refer to Circuit Testing 
and Wiring Repairs in Wiring Systems. 
Did you find and correct the condition?

-

Go to 

Step 8

Go to Step 6

5

Repair the 4WD low signal circuit for short to voltage. 
Refer to Wiring Repairs in Wiring Systems. 
Did you find and correct the condition?

-

Go to 

Step 8

-

6

Replace the PCM. Refer to Powertrain Control Module 
(PCM) Replacement in Engine Controls 6.0L (LQ4). 
Did you complete the repair?

-

Go to 

Step 8

-

7

Replace the transfer case shift control module. Refer to 
Transfer Case Shift Control Module Replacement . 
Did you complete the repair?

-

Go to 

Step 8

-

8

1. Use the scan tool in order to clear the DTCs.  

2. Operate the vehicle within the Conditions for 

Running the DTC as specified in the supporting 
text.  

-

 

2004 Hummer H2 

2004 DRIVELINE/AXLE Transfer Case - BW 4484 - Hummer H2

  

DTC C0550 

Circuit Description 

At each power-up the transfer case shift control module runs a self-test on the following functions: 

z

EEPROM Checksum  

z

ROM Checksum  

z

RAM Checksum  

z

RAM Malfunction  

Conditions for Running the DTC 

z

The ignition is ON.  

z

The system voltage is 9-18 volts.  

Conditions for Setting the DTC 

z

Critical operational parameters stored in EEPROM have failed Checksum test indicating invalid data.  

z

Masked ROM code has failed Checksum test indicating that masked ROM data is not currently valid.  

z

ROM code has failed Checksum test indicating that ROM data is not currently valid.  

z

One or more ROM locations have failed operational test indicating that some portions of RAM are not 
functional.  

Action Taken When the DTC Sets 

z

The SERVICE 4WD indicator will be latched on and the system will be disabled.  

z

The transfer case control switch will display the current position LED while DTC C0550 is current, but 
further shifting will be disabled.  

Conditions for Clearing the DTC 

z

Replace the transfer case shift control module.  

z

Perform the Transfer Case Diagnostic System Check.  

Test Description 

The number below refers to the step number on the diagnostic table. 

2: This step replaces the transfer case shift control module. 

Does the DTC reset?

Go to 

Step 2

System OK

 

2004 Hummer H2 

2004 DRIVELINE/AXLE Transfer Case - BW 4484 - Hummer H2