Transfer Case - Bw 4484: Overview Hummer H2 I

Test Description

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

1. 2: Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
2. 3: A fuse failure will cause no communication this step has you check for this condition.
3. 4: This step determines if the fuse blows when the ignition is turned on.
4. 5: This step determines if there is a short to ground in the battery positive circuit causing the fuse to blow.
5. 6: This step refers to the table for DTC C0306 for further diagnosis if a transfer case mode change is causing the fuse to blow.
6. 7: The presence of DTCs indicates that the transfer case shift control module has detected a fault. Go to symptoms for other concerns.
7. 8: The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.
8. 9: Vehicle speed is provided to the transfer case shift control module via Class 2 and can effect the setting of DTC C0300. Perform the diagnostics for powertrain DTCs P0502 and P0503 first.

Diagnostic System Check - Transfer Case

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

1. 2: This step tests for voltage at the ignition 3 voltage side of the transfer case select switch.
2. 3: This step tests the control circuit of the neutral indicator for a short to voltage or an open.
3. 4: This step tests the control circuit of the neutral indicator for a short to ground.

DTC B0790

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

1. 2: This step tests for proper operation of the transfer case mode select switch.
2. 3: This step tests the mode switch for proper resistance values in all mode switch states.
3. 4: This step tests for proper voltage on the 5 volt reference circuit.
4. 5: This step tests the 5 volt reference circuit for an open, high resistance, short to voltage, or short to ground.
5. 6: This step tests the switch signal circuit for an open, high resistance, short to voltage, or short to ground.

DTC B2725

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

1. 2: This step tests motor A driver high for proper operation.
2. 3: This step tests motor B driver high for proper operation.
3. 4: This step tests motor A driver low for proper operation.
4. 5: This step tests motor B driver low for proper operation.
5. 6: This step tests motor control A and motor control B circuits for being shorted together.
6. 7: This step tests motor control A for a short to ground, short to voltage, open, or high resistance.
7. 8: This step tests motor control B for a short to ground, short to voltage, open, or high resistance.

DTC C0306

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

1. 2: This step determines if 2 or more of the 5 volts encoder signal circuits are shorted together.
2. 3: This step tests for proper voltage on the 4 encoder signal circuits.
3. 4: This step tests for a short to voltage, open, or high resistance on the encoder low reference circuit.
4. 5: This step determines which encoder signal circuits are shorted together.
5. 6: This step determines if any of the encoder signal circuits have an open, or high resistance condition.
6. 7: This step determines if a binding shift detent lever shaft is causing the DTC.

DTC C0327

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

1. 2: This step determines if one or more of the encoder channel circuits are shorted to ground.
2. 3: This step checks with a digital multimeter (DMM) for a short to ground on any of the 4 encoder channel circuits.
3. 4: This step checks the encoder sign return circuit for a short to ground.
4. 5: This step determines if a faulty transfer case shift control module is causing the DTC to set.
5. 6: This step determines if the encoder motor is causing the DTC to set.

DTC C0329

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

1. 2: This step tests for proper reference voltage to the transfer case shift control module on the 4WD low signal circuit.
2. 3: This step tests the 4WD low signal circuit for a short to voltage.
3. 4: This step tests the 4WD low signal circuit for an open or high resistance.
4. 5: This step repairs the 4WD low signal circuit for a short to voltage.

DTC C0359

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

1. 2: This step replaces the transfer case shift control module.

DTC C0550

Symptoms - Transfer Case

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

1. 2: This step tests the functionality of the mode switch.
2. 3: This step tests the modules ability to operate the transfer case modes.

Transfer Case Shift Control Switch Inoperative

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

1. 2: This step tests the transfer case electrical control of the lamp circuits.
2. 3: This step tests the suspect lamp circuits for a short to ground.

Transfer Case Shift Control Switch Indicator Always On - Two or More

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

1. 2: This step tests for the possibility of a missing system input or a system fault.
2. 3: This step tests for a missing PRNDL input from the transmission.
3. 4: This step tests for a missing VSS signal from the ABS system.
4. 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

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

1. 2: This step determines if the module can command the indicators ON.
2. 3: This step determines if the indicator or wiring is at fault.
3. 4: This step tests the lamp feed circuit for an open or high resistance.
4. 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

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

1. 2: This step determines whether the failure is the result of a malfunctioning transfer case shift control module or the IPC.

Service Indicator Always On

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

1. 2: This step determines whether the failure is the result of a faulty transfer case shift control module or the IPC.

Service Indicator Inoperative

Transfer Case Description and Operation

The Borg Warner (BW) model 4484 NR4 transfer case is a two-speed, full time 4WD, transfer case. The transfer case has an external planetary type differential, which has two different sets of pinion gears. The planetary differential provides a 40/60 torque split front/rear full time. This means the front and rear propeller shafts are constantly being driven for maximum traction in all conditions. A high/low planetary carrier assembly provides the high and low ranges, which is a 6-pinion gear, sun gear, and annulus gear arrangement giving a 2.64 low range reduction ratio.

The BW 4484 case halves are high-pressure die-cast magnesium. Ball bearings support the input shaft, the front output shaft, and the rear output shaft. A needle roller bearing is located inside of the input shaft gear to support the front of the mainshaft. The rear of the mainshaft is supported by a bronze bearing inside the rear output shaft. The transfer case requires DEXRON III ATF Fluid GM P/N 12346143 (Canadian P/N 10952622), which is red in color. An oil pump pumps the fluid through the mainshaft oil gallery to the gears and bearings.

Scheme 24

The BW 4484 transfer case features a 4-button shift control switch located on the instrument panel. When the vehicle has the ignition key in the RUN position, the transfer case shift control module starts monitoring the transfer case shift control switch to determine if the driver desires a new mode/gear position. At a single press of the transfer case shift control switch, the lamp of the new desired position begins flashing to inform the driver that the transfer case shift control module has received the request for a new mode/gear position. The lamp continues to flash until all shifting criteria have been met and the new mode/gear position has been reached, or has been engaged. Once the new mode/gear position is fully active, the switch indicator lamp for the new position remains ON constantly.

During normal driving situations, the transfer case operates in the 4HI mode. When the 4HI mode is selected, the transfer case shift control module sends 12 volts to an electrical motor, which is the transfer case encoder motor. This motor rotates the transfer case shift detent lever shaft which moves the shift forks and range sleeve to obtain different modes/ranges.

The BW 4484 transfer case has the added feature of also providing the driver with 3 manual mode/range positions

1. 4HI - 4 Wheel Drive High Open
2. 4HI Lock - 4 Wheel Drive High Locked
3. 4LO Lock - 4 Wheel Drive Low Locked

The driver may choose to select any of these mode/range positions while driving the vehicle. However, the transfer case will not allow a shift into or out of 4LO Lock unless the following criteria has been met

1. The engine is running.
2. The automatic transmission is in Neutral.
3. The vehicle speed is below 5 km/h (3 mph).

This transfer case also has a Neutral position. A shift to the Neutral position allows the vehicle to be towed without the transmission output shaft rotating. Refer to the Owners Manual for instructions for proper towing of the vehicle.

Neutral position may be obtained only if the following criteria have been met

1. The engine is running or the ignition is ON.
2. The automatic transmission is in Neutral.
3. The vehicle speed is below 5 km/h (3 mph).
4. The transfer case is in the 4HI mode.

Once these conditions have been met, press and hold both the 4HI and 4LO Lock buttons for 10 seconds. When the system completes the shift to Neutral, the red Neutral indicator illuminates.

The BW 4484 transfer case has one other additional feature along with the 3 modes. The Electronic Rear Differential Lock can only be used in the 4LO Lock mode with a vehicle speed at or below 32 km/h (20 mph).

Scheme 25

When the BW 4484 is in 4HI mode, the engine power flows from the transmission to the input shaft (1). The input shaft (1) is connected to the mainshaft (3) by the high/low range sleeve (2). The high/low range sleeve (2) outer teeth are engaged with the input shaft (1) high-speed teeth. The range collar is slip splined to the mainshaft (3). The mainshaft (3) delivers the power flow to the planetary differential (6), which splits the torque 40 percent through the front differential pinion gears (5) to the front sun gear (10). The torque to the front axle then goes through the drive sprocket (4), via the chain (11) to the front output shaft (12) and to the front axle. The differential planetary splits the torque 60 percent to differential rear pinion gears (9) and rear sun gear (7). The rear sun gear is connected to the rear output shaft (8) and the torque flows to the rear axle. In the 4HI mode, if traction is lost to one axle and the tires spin, the Traction Assist System (TAS) applies braking to the spinning tires and the engine power is delivered to the other tires.

Scheme 26

When shifting to the 4HI Lock mode, the encoder motor (4) turns the shift detent lever shaft (5), to rotate the shift detent lever cam (8). The cam action of the shift detent lever cam (8) moves the lockup mode shift fork rearward along with the lockup shift assembly sleeve (2). The lockup shift assembly sleeve (2) locks the mainshaft (1) to the drive sprocket (3). Torque is sent by the chain (6) to the front output shaft (7) and to the front axle. The torque distribution in this mode is now determined by vehicle dynamic conditions and weight distribution. The planetary differential is not operating, and both the front and rear propeller shafts are being driven at equal RPMs, therefore giving a 4 high lock mode. This mode should only be used for extra traction during off road use. Using this mode on dry pavement causes tire scuffing.

Scheme 27

When shifting the transfer case to the 4LO Lock mode, it commands the encoder motor (7) to turn the shift detent lever shaft (8), to rotate the shift detent lever cam (9). The range cam profile on the shift detent lever cam (9) moves the high/range shift fork (10) and the high/low range sleeve (4) rearward to the 4LO Lock range position. The high/low range sleeve (4) outer teeth disengage from the input shaft (1) high-speed teeth. The high/low range sleeve (4) outer teeth then engage in the high/low planetary carrier teeth (11). The power flow is now from planetary teeth on the input shaft (1) to the planetary gears (2) in the carrier. Rotating the planetary gears, which are engaged in the annulus gear (3), rotates the planetary carrier. The planetary carrier delivers the power to the high/low range sleeve (4). The high/low range sleeve (4) then drives the mainshaft (5), providing a 2.64:1 reduction to the speed of the mainshaft (5). When in the 4LO Lock position, the lockup mode shift fork and lockup shift assembly (6) engages in the same way as in the 4HI Lock mode.