System Outline

The 4WD ECU operates the 2-4 select motor in accordance with the conditions of the 2-4 select SW, detection SW (Transfer Position) and detection SW (Transfer L4 position). It also controls the range over which shifting from H2 to H4 is possible based on the Oil Temp. Sensor and Vehicle Speed Sensor [Comb. Meter]. If the 2-4 select SW is pushed in while shifting is prohibited, it causes the 4WD indicator light [Comb. Meter] to flash and sounds a warning buzzer to inform the driver. The warning buzzer is built into the ECU. The operation of the ECU is as follows.

2-4 SELECT SYSTEM
The 2-4 select system selects between 2WD and 4WD by means of a 2-4 select SW located in the transfer shift lever knob which provides good operability.

This system uses an ECU which drives the 2-4 select motor in accordance with signals from various sensors and accomplishes shifting between 2WD and 4WD. Shifting between H4 and L4 is accomplished by operating the transfer shift lever as before. This system also permits shifting between H2 and L4 without first shifting to H4. All models equipped with the 2-4 select system are also equipped with ADD, explained later.

1. Shifting from H4 to H2
When the 2-4 select SW is turned OFF, a signal is input to the 2-4 select motor from the 4WD ECU, activating the 2-4 select motor so that the transfer changes to 2WD (H2 position)

At this time, The transfer 4WD position SW and ADD indicator SW are OFF, So the 4WD indicator light [comb. meter] goes OFF.

2. Shifting from H2 to H4 (during normal driving)
When the 2-4 select SW is turned ON, a signal is input to the 2-4 select motor from the 4WD ECU, Activating the 2-4 select motor so that the transfer changes to 4WD (H4 position)

3. Shifting from H2 to H4 (when shifting prohibited)
During cold engine conditions, Shifting from H2 to H4 may not occur smoothly due to high viscosity of the oil in the transfer. For this reason shift prohibition is applied in cold engine conditions.

When shifting prohibition occurs, the 4WD ECU stops the signal to the 2-4 select motor in accordance with the signals from the Oil Temp. Sensor and the Speed Sensor [Comb. Meter]. At the same time, it causes the 4WD indicator light [comb. meter] to light up and the warning buzzer inside the 4WD ECU to sound.

Shift prohibition stops when the oil temperature inside the ADD reaches a set temperature.

4. Shifting to L4
When the transfer shift lever is moved to L4 position, the transfer changes to LO position. This turns the detection SW (transfer L4 position) ON, so regardless of whether the 2-4 select SW is ON or OFF, a signal is input to the 2-4 select motor from the 4WD ECU, activating the 2-4 select motor so that the transfer changes to 4WD (L4 position) in LO condition.