Hummer H2. Manual - part 2657

TRANSFER CASE SHIFT CONTROL SWITCH INDICATOR FLASHES, THEN RETURNS TO
PREVIOUS MODE

Circuit Description

The transfer case shift control module flashes each indicator lamp after a shift has been requested and continues
to flash until the transfer case shift control module can complete the shift. If the transfer case is unable to make
a shift, the requested mode indicator flashes and returns to the previous mode. If the requested mode indicator
flashes for 15 seconds and returns to the previous mode, this indicates the loss of a necessary input from another
module. The transfer case shift control module requires a vehicle speed sensor (VSS) signal, provided by the
ABS module, and a PRNDL input provided by the transmission. These signals are provided to the transfer case
shift control module via class 2, and if not received the transfer case will not shift.

Do all the lamps go OFF?

Step 7

Go to Step 3

1. Use the scan tool in order to determine the transfer case

mode.

2. Use this information to determine which lamp circuits

are at fault.

3. Disconnect the mode switch.

4. Test the suspect lamp circuits for a short to ground.

Refer to Circuit Testing and Wiring Repairs in
Wiring Systems.

Is the suspect circuit shorted to ground?

Go to

Step 4

Go to Step 6

1. Disconnect the transfer case shift control module.

2. Test the suspect lamp circuits for a short to ground.

Refer to Circuit Testing and Wiring Repairs in
Wiring Systems.

Is the suspect circuit shorted to ground?

Go to

Step 5

Go to Step 7

Repair short to ground in the suspect lamp circuit. Refer to
Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?

Go to

Step 8

Replace the mode switch. Refer to Transfer Case Shift
Control Switch Replacement .
Is the repair complete?

Go to

Step 8

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

Go to

Step 8

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

2. Operate the vehicle in order to determine if the

symptom has been corrected.

Is the symptom still present?

Go to

Step 2

System OK

2004 Hummer H2

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

If a new mode is requested and the requested mode indicator flashes less then 15 seconds and returns to the
previous mode, this indicates a transfer case fault. This symptom is caused by an internal mechanical transfer
case fault causing the shift detent lever shaft to bind, or a fault within the encoder motor.

Test Description

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

2: This step tests for the possibility of a missing system input or a system fault.

3: This step tests for a missing PRNDL input from the transmission.

4: This step tests for a missing VSS signal from the ABS system.

5: This step determines if the condition is caused by a faulty encoder motor or a mechanical internal fault
to the transfer case.

Transfer Case Shift Control Switch Indicator Flashes, then Returns to Previous Mode

Step

Action

Yes

Schematic Reference: Transfer Case Control Schematics
Connector End View Reference: Transfer Case Control Connector End Views

Did you perform the Diagnostic System
Check - Transfer Case?

Go to Step 2

Go to Diagnostic System

Check - Transfer Case

1. Turn ON the ignition, with the engine

OFF.

2. Place the vehicle in Neutral.

3. Select a different mode on the transfer

case shift control switch.

Does the switch flash the full 15 seconds?

Go to Step 3

Go to Step 5

1. Connect a scan tool to the vehicle.

2. Test for transmission DTCs indicating

loss of the PRNDL signal.

Is a DTC set?

Go to Diagnostic

Trouble Code

(DTC) List/Type

Go to Step 4

With the scan tool, test for ABS DTCs
indicating a loss of VSS.
Is a DTC set?

Go to Diagnostic

Trouble Code

(DTC) List

Go to Testing for Intermittent

Conditions and Poor

Connections in Wiring

Systems

1. Remove the transfer case encoder

motor, while leaving the electrical
harness connected.

2. Attempt to shift the transfer case to a

different mode.

Is the encoder motor able to make the shift?

Go to Step 7

Go to Step 6

2004 Hummer H2

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

TRANSFER CASE SHIFT CONTROL SWITCH INDICATOR INOPERATIVE - ONE OR MORE

Circuit Description

The indicator lamps circuit consist of five individual lamps contained inside the mode switch assembly. They
are 4HI, 4HI Lock, 4LO Lock, Neutral, and Differential Lock. The 4HI, 4HI Lock, 4LO Lock, and Differential
Lock, are contained inside their respective mode button. When the ignition in ON, the transfer case shift control
module illuminates the indicator lamp that corresponds to the current ATC gear position by providing a ground
through a current limiting driver.

The transfer case shift control module flashes each indicator lamp after a shift has been requested and will
continue to flash until the transfer case shift control module can complete the shift.

A solid state circuit located inside the switch supplies ignition voltage to the lamps. The solid state circuit also
receives voltage whenever the headlamp switch is in the parklamp or headlamp position. When the solid state
circuit receives voltage from the headlamp switch it will reduce the voltage that it supplies to the indicator
lamps, dimming the lamps when the headlamps are ON.

Test Description

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

2: This step determines if the module can command the indicators ON.

3: This step determines if the indicator or wiring is at fault.

4: This step tests the lamp feed circuit for an open or high resistance.

5: This step tests the LED dimming circuit for an open or short to ground.

Transfer Case Shift Control Switch Indicator Inoperative - One or More

Replace the transfer case encoder motor.
Refer to Transfer Case Motor/Encoder
Replacement .
Is the repair complete?

Go to Step 8

Remove the transfer case and repair, for a
shift detent lever shaft binding condition.
Refer to Transfer Case Disassemble .
Is the repair complete?

Go to Step 8

1. Use the scan tool in order to clear the

DTCs.

2. Operate the vehicle in order to

determine if the symptom has been
corrected.

Is the symptom still present?

System OK

Step

Action

Yes

2004 Hummer H2

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

Schematic Reference: Transfer Case Control Schematics
Connector End View Reference: Transfer Case Control Connector End Views

Did you perform the Diagnostic System Check -
Transfer Case?

Go to Step 2

Go to Diagnostic

System Check -

Transfer Case

1. Turn ON the ignition, with the engine

OFF.

2. Install a scan tool.

3. Use the scan tool in order to command all

the indicator lamps ON.

Do all the lamps turn ON?

Go to Testing for

Intermittent Conditions

and Poor Connections

Go to Step 3

1. Access the back of the mode switch.

2. Using a fused jumper back probe the

effected indicator control circuit to
ground.

Does the effected lamp turn ON?

IMPORTANT:

Do not damage a connector or circuit when
back probing.

Go to Step 4

Go to Step 5

Test the effected indicator control circuit 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 8

Go to Step 7

Test the LED dimming circuit for an open or
short to ground. Refer to Circuit Testing and
Wiring Repairs in Wiring Systems.
Was the condition found and corrected?

Go to Step 8

Go to Step 6

Replace the mode switch. Refer to Transfer
Case Shift Control Switch Replacement .
Is the repair complete?

Go to Step 8

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

Go to Step 8

1. Use the scan tool in order to clear the

DTCs.

2. Operate the vehicle in order to determine

if the symptom has been corrected.

Is the symptom still present?

Go to Step 2

System OK

2004 Hummer H2

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

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