System Outline
Depending on the transfer shift actuator status and the ADD actuator status, the 4WD control ECU drives the transfer shift actuator and the ADD actuator to electrically change the gear position selected by the driver according to vehicle speed signal and the park/neutral position SW signal.
- Shift Select Control
Shifting from the H2 to H4 position
When the 4WD control switch is turned from H2 to H4, this signal is input into the 4WD control ECU (TERMINAL 2-4). Then, the 4WD control ECU moves the 2-4 select motor (TERMINAL 2, TERMINAL 1) in the transfer shift actuator until the shift fork shaft shifts to the diff. Free position, performing a shift into H4 position
Switching diff. Lock ON when in the H4 position.
When the diff. Lock switch is turned ON and the 4WD control switch is in the H4 position, this signal is input into the 4WD control ECU (TERMINAL DL). Then, the 4WD control ECU drives the 2-4 select motor (TERMINAL 2, TERMINAL 1) in the transfer shift actuator until the shift fork shaft shifts to the diff. Lock position, locking it in the H4 position with the diff. lock.
Shifting from the H4 to L4 position
When the 4WD control switch is turned from H4 to L4, this signal is input into the 4WD control ECU (TERMINAL LO). Then, the 4WD control ECU drives the H-L select motor (TERMINAL 8, TERMINAL 7) in the transfer shift actuator, shifting the shift fork shaft, performing a shift into L4 position.
Switching diff. Lock ON when in the L4 position.
When the diff. Lock switch is turned ON and the 4WD control switch is in the L4 position, this signal is input into the 4WD control ECU (TERMINAL DL). Then, the 4WD control ECU drives the 2-4 select motor (TERMINAL 2, TERMINAL 1) in the transfer shift actuator until the shift fork shaft shifts to the diff. Lock position, locking it in the L4 position with the diff. lock.
- Function of Limit Switch
H4L limit switch (TERMINAL 12 and TERMINAL 11 of transfer shift actuator)
The H4L limit switch in the transfer shift actuator feeds back the current shift position status (H4 or L4) information, which is based on the ON/OFF combination of the two switches, to the 4WD control ECU.
4WD limit switch (TERMINAL 3, TERMINAL 4 and TERMINAL 5 of transfer shift actuator)
The 4WD limit switch in the transfer shift actuator feeds back the current shift position status (H2 or H4) and diff. Lock or diff. Free status information, which is based on the ON/OFF combination of the three switches, to the 4WD control ECU.
ADD limit switch (TERMINAL 6 and TERMINAL 2 of ADD actuator)
The ADD limit switch in the ADD actuator feeds back the current front diff. Lock or free status information, which is based on the ON/OFF combination of the two switches, to the 4WD control ECU.
- Shift Limit Control
The 4WD control ECU interrupts the shift select control and gives the driver a warning by sounding the buzzer (Integrated into the ECU) and blinking the indicator light on the combination meter when the following shift change conditions exist.
The warning, however, will be canceled if the 4WD control switch is canceled and the switch position is returned to where it was before the warning occurred.
* A shift change from H2 into H4 is attempted while the vehicle is traveling at or exceeding a speed of 100 km/h (Buzzer sound and blinking 4WD and center diff. Lock indicator lights)
* A shift change from H4 into L4 is attempted while the vehicle is traveling at or exceeding a speed of 5 km/h but within the A/T shift position N range (Buzzer sound and blinking L4 indicator light)
- ADD Actuator Control
When switching between H2 (2WD) and H4 (4WD), the 4WD control ECU controls the way power is supplied to the ADD motor in the ADD actuator, as shown below, to run the ADD motor in the normal or reverse direction, thereby changing the status of the front diff. From free to lock, or vice versa.
For locking front diff.
TERMINAL DM1 +B
TERMINAL DM2 GROUND
For unlocking front diff.
TERMINAL DM1 GROUND
TERMINAL DM2 +B