System Description
System Description
CONTROL SYSTEM
ALL-MODE 4WD Transfer Basic Control
Hydraulic Control Circuits
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.
Table 1
Table 2
^ 4WD shift switch, PNP switch, Neutral-4LO switch, vehicle speed sensor and throttle position sensor are used in conjunction with the transfer motor.
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.
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.
ATP SWITCH
ATP switch detects if transfer gear is in a neutral condition by L-H shift fork position.
NOTE: Transfer gear may be in a neutral condition in 4H-4LO.
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.
CLUTCH PRESSURE SOLENOID VALVE
The clutch pressure solenoid valve distributes torque (front and rear) in AUTO mode.
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 turns ON 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 turns ON when clutch pressure is produced.
^ The clutch pressure switch senses clutch pressure abnormalities and turns the 4WD warning lamp ON.
TRANSFER FLUID TEMPERATURE SENSOR
The transfer temperature sensor detects the transfer fluid temperature and sends a signal to the transfer control unit.
TRANSFER CONTROL UNIT
^ Transfer control unit controls transfer control device by input signals of each sensor and each switch.
^ Self-diagnosis can be done.
TRANSFER CONTROL DEVICE
The transfer control device changes the state of transfer assembly between 2WD, AUTO, 4H<4LO with the 2WD, AUTO, 4H and 4LO signals of 4WD shift switch.
NOTE:
^ To shift between 4H 4LO, stop the vehicle, depress the brake pedal and shift the transmission selector to the "N" position. Depress and turn the 4WD shift switch. The shift switch will not shift to the desired mode if the transmission is not in "N" or the vehicle is moving. The 4LO indicator lamp will be lit when the 4LO is engaged.
^ Actuator motor and actuator position switch are integrated.
4WD SHIFT SWITCH AND INDICATOR LAMP
4WD Shift Switch
The 4WD shift switch allows selection 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 FLASH when there is a malfunction in 4WD system.
Also turns ON when ignition switch is turned ON, for purpose of lamp check. Turns OFF for approximately 1 second after the engine starts if system is normal.
4WD Warning Lamp Indication
ATP WARNING LAMP
Even if A/T selector lever is in "P" position, vehicle may move because A/T parking mechanism does not operate when transfer is under neutral condition. ATP warning lamp is turned on so as to indicate this condition to the driver.