GENERAL INFORMATION

Electronic control 4WD has been adopted to ensure the on-road performance, achieve lighter and smaller body, and realize better fuel economy.
The electronic control 4WD controls the torque of the electronic control coupling located between the propeller shaft and rear differential. This strategy is enabled by varying the torque distribution to the front and rear wheels from the status closer to the front wheel drive to the status closer to the direct coupling 4WD and realizes the optimal drive force according to the various driving conditions.

AIMS OF DEVELOPMENT

Lightweight and simple construction of the electronic control 4WD achieves good fuel efficiency and provides enjoyment of selecting the drive mode.

FUNCTION

The adoption of the electronic control coupling prevents the tight corner braking phenomenon^* and satisfies the traction performance.

note

^*Tight corner braking indicates the following condition. When the 4WD vehicle turns sharply on a pavement at low speed (ex. parallel parking), the rotational radius of the front and rear wheels differs, and this difference can no longer be compensated by the tyre slippage. At this time, the driver feels as if the brake was applied.

The electronic control 4WD receives the signals of the throttle position and vehicle speed via CAN^* communication protocol, detects the vehicle driving condition and operation of the driver, and distributes the proper torque to the rear wheels.

note ^*: For more information about CAN (Controller Area Network), refer to GROUP 54C .
Under severe driving condition, the system is protected by minimizing the limitation force of the differential.
During high-speed driving, the fuel efficiency is improved by reducing the limitation force of the differential.
The following drive modes are available according to the drivers’ preference to provide the enjoyment of selecting functions.

Drive mode	Control content	Appeal points
2WD	Minimizes the limitation force of the differential.	High fuel efficiency mode which enables smoother turning performance of the FF vehicle
4WD	Increases the limitation force of the differential according to the different rotation speed of the front and rear wheels and the throttle position.	Universal mode which automatically distributes the drive force to the rear wheels as necessary
LOCK	Further increases the limitation force of the differential compared to the 4WD mode.	Mode which has an excellent driving performance when driving on rough road or in stuck situation and enables the powerful driving

CONSTRUCTION DIAGRAM

System component and function

Parts name	Functional description
Engine ECU	Sends the following signals required by 4WD-ECU via CAN communication. Engine torque signal Throttle position signal Engine speed signal
ASC-ECU	Sends the following signals required by 4WD-ECU via CAN communication. ABS sensor signal (wheel speed signal) [4 wheels] ABS operation signal 4WD limitation torque signal
Drive mode selector	Sends the drive mode switch signal [2WD/4WD/LOCK] to 4WD-ECU.
ETACS-ECU	Receives the drive mode switch signal [2WD/4WD/LOCK] from 4WD-ECU and flashes the indicators (4WD operation indicator and LOCK indicator) in the combination meter. Flashes the indicators (4WD operation indicator and LOCK indicator) in the combination meter in case of failure.
ETACS-ECU	Controls diagnostic function (Compatible with M.U.T.-III).
4WD-ECU	Calculates the optimum differential limitation force judging from the vehicle condition and present drive mode based on the signals from each ECU and switch, and controls the current value flown to the electronic control coupling.
	Controls the indicators (4WD operation indicator and LOCK indicator) in the combination meter.
	Controls the self-diagnostic function and fail-safe function.
	Controls diagnostic function (Compatible with M.U.T.-III).
Electronic control coupling	Transmits the torque corresponding to the current value controlled by 4WD-ECU to the rear wheels.
Drive mode indicator 4WD operation indicator LOCK indicator	Integrated in the combination meter, and indicates the selected drive mode (Not displayed in 2WD mode). When the 4WD operation indicator and LOCK indicator flash alternately, the system automatically enters the front wheel drive mode to protect the drive system components, and the drive mode changeover with the drive mode selector becomes unavailable. When the drive system generates heat, the 4WD operation indicator flashes. The indicator lamp operation signal from 4WD-ECU is sent to the combination meter via ETACS-ECU using CAN communication.
Diagnosis connector	Outputs the diagnosis code and establishes the communication with M.U.T.-III.

GENERAL INFORMATION

AIMS OF DEVELOPMENT

FUNCTION

CONSTRUCTION DIAGRAM

System configuration

Control schematic diagram

Electronic control 4WD electric circuit diagram