4WD Control System Components and Functions
4WD CONTROL SYSTEM COMPONENTS AND FUNCTIONS
| Component | Function |
|---|---|
| 4WD switch [A] | When the transfer shift lever is shifted to "4L" or "4H" position, this switch turns ON and causes the 4WD control system to turn ON, unless it is shifted to "N" or "2H" within 1 second. |
| ECM or PCM | When the 4WD switch turns ON [unless it turns OFF within 1 second], this component actuates the pump assembly. If the pressure in the air pump assembly fails to increase higher than the set level even after the pump motor has run more than 10 seconds, this component stops the motor to protect it. |
Air pump assembly
|
The air pump assembly consists of a pump motor, release valve and a pressure switch. Pump motor: Produces positive pressure which actuates the actuator. Release valve: Closes when transfer shift lever is shifted to "4H" or "4L" so that the positive pressure is applied to the actuator, and opens when "N" or "2H" to release the pressure to the atmosphere. Pressure switch: Turns ON and OFF depending on the pressure level in the pump assembly (whether higher or lower than the set pressure level). ECM or PCM detects the pressure level through this switch. |
Differential case assembly
|
The free axle hub, axle lock clutch and actuator are installed in the differential left case. The positive pressure produced in the pump assembly is applied to the actuator which then pushes the axle lock clutch to be engaged with the free axle hub. In this state, the drive force is transmitted to the front axle, resulting in the 4WD mode. When the actuator is free from the positive pressure [when it is under the atmospheric pressure], the axle lock clutch is pushed back by the return spring force and cannot be engaged with the free axle hub, resulting in the 2WD mode. |
| "4WD" indicator lamp [F] | It lights up when 4WD control system is in the 4WD mode. |