Circuit/System Description
The Neutral indicator circuit consists of a ignition 3 voltage circuit and a Neutral indicator control circuit. When the Neutral mode has been selected by the driver, current is supplied to the Neutral indicator by the ignition 3 voltage circuit, traveling through the Neutral indicator LED at which time the transfer case shift control module supplies the ground through the Neutral indicator control circuit. This DTC indicates an open, short to ground or a short to voltage.
The mode switch circuit consists of 4 modes. The transfer case shift control module supplies a regulated 5 volts, DC to the switch through the 5-volt regulator circuit. The current travels through the resistor of the currently selected mode. The current is then returned to the transfer case shift control module through the switch signal circuit.
The transfer case shift control module constantly monitors this signal voltage to determine the condition of the mode switch circuit.
When each of the modes are selected they will complete a circuit through their own specific resistor when a mode is selected. The transfer case shift control module continuously monitors the switch input to determine whether the Neutral, 4HI, 4HI Lock, or 4LO Lock mode was selected by the driver.
The mode switch circuit consists of 3 or 4 modes depending on how the vehicle is equipped with the transfer case shift control module only monitoring the rear differential lock portion of the switch. The transfer case shift control module supplies a regulated 5 volts, DC to the switch through the 5-volt regulator circuit. The current travels through the resistor of the currently pressed mode button. The current is then returned to the transfer case shift control module through the switch signal circuit.
The transfer case shift control module constantly monitors this signal voltage to determine the condition of the mode switch circuit.
When each of the modes are selected they will complete a circuit through their own specific resistor while the button is pressed. The transfer case shift control module continuously monitors the switch input to determine if the Differential Lock mode was selected by the driver.
The transfer case motor is a bi-directional, permanent magnet, D.C. motor. When energized, through motor control A or motor control B, the ground is provided by the opposing motor control circuit and then grounded through the transfer case shift control module ground circuit, the motor, through a series of gears, rotates a shaft which moves the mode and range forks to shift the transfer case between the following ranges
- 4HI
- 4HI Lock
- 4LO Lock
- Neutral
This DTC detects an open, short to voltage, or short to ground in the motor control A or motor control B circuits, or an open, or short to ground inside the motor.
The transfer case shift control module has four encoder channels, P, C, A, and B, which are supplied 5 volts each. The four encoder channels each run to a switch located inside the encoder/motor assembly. When a particular encoder channel is active the switch is closed and 5 volts flows through the encoder signal return circuit. If the module wants to request motor position a low side driver pulls the voltage low on the encoder signal return and the corresponding channel circuit indicating motor position.
The transfer case shift control module supplies 5 volts on all encoder channels, thus as these channels are pulled to ground, the module can interpret the location of the transfer case shift position.
This DTC detects an open, high resistance, or a short to voltage, in the encoder signal return circuit, or an open, high resistance, or short to voltage in the encoder channel circuits.
The transfer case shift control module has 4 encoder channels coming out of it which are all supplied 5 volts. These 4 channels are P, C, A, and B, each running to a switch located inside the encoder/motor assembly. When a particular encoder channel is active, the switch is closed and 5 volts flows through the encoder signal return circuit. If the module wants to request motor position, a low side driver pulls the voltage low on the encoder signal return and the corresponding channel circuit indicating motor position.
The transfer case shift control module supplies 5 volts on all the channels. As these channels are pulled to ground, the module can interpret the location of the transfer case shift position.
This DTC detects a short to ground in the encoder signal return circuit, or a short to ground in the encoder channel circuits.
The 4WD low 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 circuit.
At each power-up the transfer case shift control module runs a self-test on the following functions
- EEPROM Checksum
- ROM Checksum
- RAM Checksum
- RAM Malfunction
Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step tests the functionality of the mode switch.
- 3: This step tests the modules ability to operate the transfer case modes.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Transfer Case Control Schematics Connector End View Reference: Component Connector End Views | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle |
| 2 | Install a scan tool. Start the engine. Place the transmission into Neutral. Set the park brake. Observe the Mode Switch Selected parameter on the scan tool while selecting each of the mode positions on the switch. Does the state change with the selection of each of the mode positions? | Go to Step 5 | Go to Step 3 |
| 3 | Test the switch signal and 5-volt reference circuits for an open, high resistance, short to ground, and short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 6 | Go to Step 4 |
| 4 | Replace the mode selection switch. Refer to Transfer Case Shift Control Switch Replacement . Did you complete the repair? | Go to Step 6 | |
| 5 | Replace the transfer case shift control module. Refer to Control Module References for replacement, setup and programming. Did you complete the repair? | Go to Step 6 | |
| 6 | Use the scan tool in order to clear the DTCs. Operate the vehicle in order to determine if the symptom has been corrected. Is the symptom still present? | Go to Step 2 | System OK |
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step tests the transfer case electrical control of the lamp circuits.
- 3: This step tests the suspect lamp circuits for a short to ground.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Transfer Case Control Schematics Connector End View Reference: Component Connector End Views | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle |
| 2 | Turn the ignition ON, with the engine OFF. Install a scan tool. Use the scan tool in order to command all the indicator lamps OFF. Do all the lamps go OFF? | Go to Step 7 | Go to Step 3 |
| 3 | Use the scan tool in order to determine the transfer case mode. Use this information to determine which lamp circuits are at fault. Disconnect the mode switch. Test the suspect lamp circuits for a short to ground. Refer to Circuit Testing and Wiring Repairs . Is the suspect circuit shorted to ground? | Go to Step 4 | Go to Step 6 |
| 4 | Disconnect the transfer case shift control module. Test the suspect lamp circuits for a short to ground. Refer to Circuit Testing and Wiring Repairs . 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 . 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 Control Module References for replacement, setup and programming. Is the repair complete? | Go to Step 8 | |
| 8 | Use the scan tool in order to clear the DTCs. Operate the vehicle in order to determine if the symptom has been corrected. Is the symptom still present? | Go to Step 2 | System OK |
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.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Transfer Case Control Schematics Connector End View Reference: Component Connector End Views | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle |
| 2 | Turn ON the ignition, with the engine OFF. Place the vehicle in Neutral. 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 | Connect a scan tool to the vehicle. Test for transmission DTCs indicating loss of the PRNDL signal. Is a DTC set? | Go to Diagnostic Trouble Code (DTC) List - Vehicle | 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 - Vehicle | Go to Testing for Intermittent Conditions and Poor Connections |
| 5 | Remove the transfer case encoder motor, while leaving the electrical harness connected. 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 |
| 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 | Use the scan tool in order to clear the DTCs. Operate the vehicle in order to determine if the symptom has been corrected. Is the symptom still present? | System OK | |
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.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Transfer Case Control Schematics Connector End View Reference: Component Connector End Views | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle |
| 2 | Turn ON the ignition, with the engine OFF. Install a scan tool. 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 | IMPORTANT: Do not damage a connector or circuit when back probing. Access the back of the mode switch. Using a fused jumper back probe the effected indicator control circuit to ground. Does the effected lamp turn ON? | 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 . 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 . 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 Control Module References for replacement, setup and programming. Is the repair complete? | Go to Step 8 | |
| 8 | Use the scan tool in order to clear the DTCs. Operate the vehicle in order to determine if the symptom has been corrected. Is the symptom still present? | Go to Step 2 | System OK |
| IMPORTANT |
|---|
| Do not damage a connector or circuit when back probing. |
The number below refers to the step number on the diagnostic table.
- 2: This step determines whether the failure is the result of a malfunctioning transfer case shift control module or the IPC.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Transfer Case Control Schematics Connector End View Reference: Component Connector End Views | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle |
| 2 | Observe the Service 4WD parameter input/output in the instrument panel cluster (IPC) Scan Tool Data List. Is the Service 4WD indicator commanded ON? | Go to Step 3 | Go to Step 4 |
| 3 | Replace the transfer case shift control module. Refer to Control Module References for replacement, setup and programming. Did you complete the repair? | Go to Step 5 | |
| 4 | Replace the IPC. Refer to Instrument Cluster Replacement . Did you complete the repair? | Go to Step 5 | |
| 5 | Use the scan tool in order to clear the DTCs. Operate the vehicle in order to determine if the symptom has been corrected. Is the symptom still present? | Go to Step 1 | System OK |
The number below refers to the step number on the diagnostic table.
- 2: This step determines whether the failure is the result of a faulty transfer case shift control module or the IPC.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Transfer Case Control Schematics Connector End View Reference: Component Connector End Views | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle |
| 2 | Observe the Service 4WD parameter input/output in the instrument panel cluster (IPC) Scan Tool Data List. Is the Service 4WD indicator commanded ON? | Go to Step 4 | Go to Step 3 |
| 3 | Replace the transfer case shift control module. Refer to Control Module References for replacement, setup and programming. Did you complete the repair? | Go to Step 5 | |
| 4 | Replace the IPC. Refer to Instrument Cluster Replacement . Did you complete the repair? | Go to Step 5 | |
| 5 | Use the scan tool in order to clear the DTCs. Operate the vehicle in order to determine if the symptom has been corrected. Is the symptom still present? | Go to Step 1 | System OK |
Transfer Case Description and Operation
The Borg Warner (BW) model 4484 NR4 transfer case is a 2-speed, full-time 4WD, transfer case. The transfer case has an external planetary type differential, which has 2 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 manual transmission fluid GM P/N 88861800 (Canadian P/N 88861801), which is red in color. An oil pump pumps the fluid through the mainshaft oil gallery to the gears and bearings.
Scheme 1
The BW 4484 transfer case features a 4-button shift control switch located on the instrument panel. When the ignition key is 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
- 4HI - 4 Wheel Drive High Open
- 4HI Lock - 4 Wheel Drive High Locked
- 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
- The engine is running.
- The automatic transmission is in NEUTRAL.
- 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
- The engine is running or the ignition is ON.
- The automatic transmission is in NEUTRAL.
- The vehicle speed is below 5 km/h (3 mph).
- 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 an 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 2
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 1 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 3
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 RPM, 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 4
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.