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
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
4
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
5
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
-
6
Replace the mode switch. Refer to Transfer Case Shift
Control Switch Replacement .
Is the repair complete?
Go to
Step 8
-
7
Replace the transfer case shift control module. Refer to
Transfer Case Shift Control Module Replacement .
Is the repair complete?
Go to
Step 8
-
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
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 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
3
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
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
5
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
6
Replace the transfer case encoder motor.
Refer to Transfer Case Motor/Encoder
Replacement .
Is the repair complete?
Go to Step 8
-
7
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
-
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
No
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
1
Did you perform the Diagnostic System Check -
Transfer Case?
Go to Step 2
Go to Diagnostic
System Check -
Transfer Case
2
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
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
4
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
5
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
6
Replace the mode switch. Refer to Transfer
Case Shift Control Switch Replacement .
Is the repair complete?
Go to Step 8
-
7
Replace the transfer case shift control module.
Refer to Transfer Case Shift Control Module
Replacement .
Is the repair complete?
Go to Step 8
-
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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