Transfer Box Control Module Inputs

The transfer box control module receives the following inputs:

• Range change selection switch
• High/low position sensor
• Transfer box actuator motor temperature
• Transfer box actuator motor position sensor
• CAN bus messages
• Gear position sensor (manual transmission only)
• Transmission output shaft speed sensor (manual transmission only).

CAN BUS MESSAGES

The CAN bus is a high speed broadcast network connected between various vehicle control modules. The CAN network carries an extensive list of messages between the different control modules enabling more sophisticated control with reduced complexity. Data on the network is packaged for efficient communication and prioritized according the urgency and importance of the Messages. The bus comprises two wires, which are twisted together to minimize electromagnetic interference (noise) produced by the CAN messages.

For additional information, refer to: COMMUNICATIONS NETWORK .

The transfer box control module is connected on the CAN bus and controls transfer box operation using CAN messages from other control units on the network. Wheel speed, vehicle acceleration, engine torque and speed, gear information, from the automatic transmission, temperature information, car configuration, axle ratios and Terrain Response™ mode inputs, are some of the main signals received by the control module.

In the event of a CAN bus failure the following symptoms may be observed:

• Shift from high to low or low to high inoperative
• Instrument cluster low range warning lamp inoperative
• warning messages or lamps displayed in instrument cluster.

GEAR POSITION SENSOR (MANUAL TRANSMISSION ONLY)

The transfer box control module uses positional information from the manual gear position sensor to determine which gear the transmission is in. This information is broadcast on the CAN bus for display on the instrument cluster and for use by other vehicle systems. Vehicles fitted with automatic transmission use a similar message broadcast by the Transmission Control Module (TCM). Vehicles fitted with manual transmission have a learning function, which compares the positional information from the sensor with the gear ratio calculated from the ratio of engine speed to transmission output shaft speed. The transmission learning is carried out at end of manufacture. If a new transmission is fitted during the life of the vehicle the learning algorithm needs to learn the characteristics of the new transmission.

The instrument cluster displays the selected gear as determined by the transfer box. The transfer box also uses this to check the vehicle is in neutral before attempting a range change.

MANUAL TRANSMISSION OUTPUT SHAFT SPEED SENSOR

The output shaft speed sensor is located at the rear of the transmission and measures the speed of the transmission output shaft.

The transfer box is designed to allow range changes when the vehicle is moving, providing the transmission speed complies with the preset thresholds determined by the control module. The control module calculates the optimized synchronization timing through the speed of the transmission output shaft and the wheel speed of the vehicle.

RANGE CHANGE SELECTION SWITCH

The range change selection switch in located behind the main transmission selection lever, in the center console. The switch is a 3-position momentary action center sprung device. The driver pushes the lever forward to select high range and back to select low range.

The switch comprises a housing, which provides the location for a sliding contact. When the switch is moved to the high or low position, it completes a momentary connection to 12V with one of two microswitches located at each end of the range change selection switch. These micro-switches correspond to the high or low range positions.

The transfer box control module receives this momentary signal and selects the requested range.

In this position, a spring will move the selector lever to the center position when released.

HIGH/LOW POSITION SENSOR

The high/low position sensor converts the pivotal movement of the high/low fork into a PWM signal on the input. The PWM signal of the position sensor differs between high range and low range. The control module checks this signal and informs the driver, via the instrument cluster and the range change selection switch LED's, if a range change is in progress or has been completed.

The high/low position sensor is connected to the transfer box control module via a three-pin connector.