Unfaulty Mode

SYSTEM DIAGRAMS

NORMAL OPERATION
The motor actuator mounted on transfer rear case is driven by signal from 4WD switch on instrument panel. After complete the connecting transfer front output gear to, or disconnecting it from, front propeller shaft, condition of the transfer position switch changes. The Vacuum Solenoid Valve (VSV) is driven by the signal from transfer position switch and the vacuum actuator connects front wheels to, or disconnect them from, front axles.





TIME CHART OF SHIFTING UNDER NORMAL CONDITION


RETRIAL
The motor actuator starts transfer gear shifting after signal from 4WD switch on instrument panel has been received. But the shifting may be impossible in cold weather or under high speed condition. When 2 seconds have passed since transfer gear shifting started and the transfer position switch does not turn on (the gear engagement is not completed), the motor reverses its rotation for 1.2 seconds and tries again to shift transfer gear. This procedure is repeated 3 times in maximum. While this procedure, 4WD indicator lamp blinks by 2Hz. If the transfer position switch does not turn on after aforementioned procedure has been repeated 3 times, the gear shifting is stopped and 4WD indicator lamp's blinking changes from 2Hz to 4Hz to notify driver that the gear shifting is stopped. This blinking of indicator lamp continues until 4WD switch is returned from 4WD to 2WD.





TIME CHART OF SHIFTING UNDER SEVERE CONDITION (RETRIAL)

Warning at "4L" position: In view of the shifting mechanism of transfer, the gear shifting from 4WD to 2WD at 'AL" condition is impossible. Therefore, the transfer position switch can not be turned off by 4WD switch when vehicle is in "4L" condition. In the case this condition continues for 2 seconds, the shifting to 2WD is stopped and the indicator lamp's blinking changes from 2Hz to 4Hz to notify driver of wrong operation.





TIME CHART OF SHIFTING FROM 4WD TO 2WD AT "4L" CONDITION





4WD out signal to other Electronic Hydraulic Control Unit: ECU of shift on the fly sends 4WD out signal to other Electronic Hydraulic Control Unit as below.


FUNCTIONS OF INDICATOR LAMP





Indication of vehicle condition: Indicator lamp is controlled by ECU of shift on the fly and shows vehicle conditions as below.

Bulb check :The bulb of indicator lamp is checked for 2 seconds when ignition key is turned on.





TIME CHART OF BULB CHECKING

Retrials from 2WD to 4WD in cold weather or under high speed condition, the gear shifting (engagement) sometimes does not complete by 3 trials. In such case, the indicator lamp inform driver of this incident as aforementioned chart (shown at Retrial in Outline of shift on the fly system.)


DIAGNOSIS
BEFORE JUDGING THAT TROUBLES OCCUR (UNFAULTY MODE)

When Switching from 2WD to 4WD
1. In case that blinking frequency of the 4WD indicator changes from 2Hz to 4Hz. When heavy synchronization load is needed, the motor actuator tries the shifting transfer gear three times including the activation shifting. While the motor actuator tries shifting, the indicator blinks by 2Hz. If the third shifting fails, the indicator's blinking changes from 2Hz to 4Hz at the same time that the motor actuator shifted back to 2WD.
Heavy synchronization load occurs by
- extremely lower temperature.
- higher speed rotation difference of wheels during cornering.
Solution 1: Operate again after stop the vehicle or slow down.
2. In case that the 4WD indicator continues blinking by 2Hz for more than 11.5 seconds. When there is rotation difference of wheels or there is phase difference between front wheels and axles, it is difficult to connect front wheels to front axles. The blinking by 2Hz shows that shifting the transfer gear or connecting the front wheels is in the middle of operating. In above case, the indicator's blinking by 2Hz shows that connecting the front wheels is not completed (because the indicator's blinking changes to 4Hz when the shifting transfer gear is impossible.). And removal of rotation or phase difference make connecting the front wheels possible.
Solution 2: When vehicle is running, drive straight ahead while accelerating and decelerating. When vehicle is at a stop, move the vehicle forward and backward from 2 to 3 meters.

When Switching from 4WD to 2WD
1. In case that the 4WD indicator continues blinking by 2Hz. The 4WD indicator continues blinking by 2Hz until both shifting the transfer gear and disconnecting the front wheels are completed when switching 4WD to 2WD. When drive line is loaded with torsional torque, the shifting transfer gear and disconnecting front wheels are impossible. In this case, removal of torsional torque on drive line make the shifting transfer gear and disconnecting front wheels possible.
Solution 3: When vehicle is running, drive straight ahead while accelerating and decelerating. When vehicle is at a stop, move the vehicle forward and backward from 2 to 3 meters.
2. In case that the 4WD indicator's blinking changes from 2Hz to 4Hz. Check the position of transfer lever. Is it at "4L" position? In view of the shifting mechanism of transfer, the gear shifting from 4WD to 2WD at "4L" condition is impossible.
Solution 4: Push the 4WD switch to 4WD, shift the transfer lever to "High" position and re-operate the 4WD switch to 2WD.