System Description
CONTROL SYSTEM
ALL-MODE 4WD Transfer Basic Control
Hydraulic Control Circuits
TRANSFER CONTROL UNIT
^ Transfer control unit controls transfer control device and it directs shifts from 4H-4LO and 2WD-4WD.
^ Self-diagnosis can be done.
TRANSFER SHIFT HIGH AND LOW RELAYS
Transfer shift high and low relays apply power supply to transfer control device (actuator motor).
TRANSFER SHUT OFF RELAY
Transfer shut off relay applies power supply to transfer motor relay
4WD SHIFT SWITCH AND INDICATOR LAMPS
4WD Shift Switch
Able to select from 2WD, AUTO, 4H or 4LO
4WD Shift Indicator Lamp
^ Displays driving conditions selected by 4WD shift switch with 2WD, AUTO and 4H indicators while engine is running. (When 4WD warning lamp is turned on, all 4WD shift indicator lamps are turned off.)
^ Turns ON for approximately 1 second when ignition switch is turned ON, for purpose of lamp check.
4LO Indicator Lamp
^ Displays 4LO condition while engine is running. 4LO indicator lamp flashes if transfer gear does not shift completely under 2WD, AUTO, 4H <----> 4LO. (When 4WD warning lamp is turned on, 4LO indicator lamp is turned off.)
^ Turns ON for approximately 1 second when ignition switch is turned ON, for purpose of lamp check.
4WD WARNING LAMP
Turns on or flashes when there is a malfunction in 4WD system.
Also turns on when ignition switch is turned ON, for purpose of lamp check. Turns OFF approximately 1 second after the engine starts if system is normal.
4WD Warning Lamp Indication
ATP WARNING LAMP
When the A/T selector lever is in P position, the vehicle may move if the transfer case is in neutral. ATP warning lamp is turned on to indicate this condition to the driver.
LINE PRESSURE SWITCH
^ With the transfer system design, control of the oil pressure provides the transmission of drive torque to the front wheels. The main pressure to control the oil pressure is referred to as the line pressure.
^ The line pressure switch determines whether or not adequate line pressure has built up under different operating conditions.
^ The line pressure switch closes when line pressure is produced.
^ The line pressure switch senses line pressure abnormalities and turns the 4WD warning lamp ON.
CLUTCH PRESSURE SWITCH
^ The clutch pressure switch determines whether or not adequate clutch pressure has built up under different operating conditions.
^ The clutch pressure switch closes when clutch pressure is produced.
^ The clutch pressure switch senses clutch pressure abnormalities and turns the 4WD warning lamp ON.
WAIT DETECTION SWITCH
^ The wait detection switch operates when there is circulating torque produced in the propeller shaft (L ---> H) or when there is a phase difference between 2-4 sleeve and clutch drum (H ---> L). After the release of the circulating torque, the wait detection switch helps provide the 4WD lock gear (clutch drum) shifts. A difference may occur between the operation of the 4WD shift switch and actual drive mode. At this point, the wait detection switch senses an actual drive mode.
^ The wait detection switch operates as follows.
- 4WD lock gear (clutch drum) locked: ON
- 4WD lock gear (clutch drum) released: OFF
^ The wait detection switch senses an actual drive mode and the 4WD shift indicator lamp indicates the vehicle drive mode.
ATP SWITCH
ATP switch detects if transfer case is in neutral by the position of the L-H shift fork.
NOTE: Transfer case may be in neutral when shifting between 4H-4LO.
NEUTRAL-4LO SWITCH
The neutral-4LO switch detects that transfer gear is in neutral or 4LO (or shifting from neutral to 4LO) condition by L-H shift fork position.
TRANSFER FLUID TEMPERATURE SENSOR
The transfer fluid temperature sensor detects the transfer fluid temperature and sends a signal to the transfer control unit.
TRANSFER MOTOR
^ The transfer motor drives the sub-oil pump to provide proper lubrication and oil pressure control when the vehicle is at standstill, during low-speed operations or is being driven in reverse.
^ The main oil pump is operated by the driving force of the mainshaft. In other words, sufficient oil pressure buildup does not occur when the vehicle is at standstill or during low-speed operations. While the vehicle is being driven in reverse, the main oil pump rotates in the reverse direction. Therefore the main oil pump does not discharge oil pressure. During any of the above vehicle operations, the transfer motor drives the sub-oil pump to compensate for insufficient oil pressure.
^ The transfer motor operates as follows:
- The motor relay turns OFF in the 2WD mode.
- The motor relay operates as described in the table below in modes other than the 2WD mode.
^ 4WD shift switch, PNP switch, NEUTRAL-4LO switch, vehicle speed sensor and throttle position sensor are used in conjunction with the transfer motor.
Transfer Motor Relay Operation
CLUTCH PRESSURE SOLENOID VALVE
The clutch pressure solenoid valve distributes front and rear torque in AUTO mode.
2-4WD SHIFT SOLENOID VALVE
The 2-4WD shift solenoid valve operates to apply oil pressure to the wet-multiplate clutch, depending on the drive mode. The driving force is transmitted to the front wheels through the clutch so the vehicle is set in the 4WD mode. Setting the vehicle in the 2WD mode requires no pressure buildup. In other words, pressure force applied to the wet-multiplate clutch becomes zero.
TRANSFER CONTROL DEVICE
Integrates actuator motor and actuator position switch.
Actuator Motor
Moves shift rods when signaled by transfer control unit.
Actuator Position Switch
Detects actuator motor position and then sends signal to transfer control unit.