2006 TOYOTA RAV4 four wheel drive

CHASSIS - 4WD SYSTEM CH-66
4WD SYSTEM
DESCRIPTION
The 4WD system of the ’06 RAV4 uses an active torque control 4WD system.
It is a compact, lightweight, and high performance 4WD system that optimally controls the torque
distribution to the front and rear wheels through the electric control coupling in the rear differential.
ACTIVE TORQUE CONTROL 4WD SYSTEM
1. General
Based on information provided by various sensors, the 4WD ECU controls the amperage that is applied
to the electric control coupling, in order to transmit drive torque to the rear wheels when needed, and in
the amount needed. The following describes the features of the active torque control 4WD system.
Traction performance
Realizes stable start-off and acceleration performance
Driving stability performanceRealizes stable cornering performance
Fuel economyRealizes better fuel economy by transmitting drive torque to the rear
wheels when needed, in the amount needed.
A four-wheel drive lock switch has been provided. This enables the driver to select between the AUTO
and LOCK modes by operating the switch. The system optimally controls the torque distribution to the
front and rear wheels in the respective modes.
Mode
Four-wheel Drive
Lock Switch and
Indicator Light
Outline
AUTOOFF
Optimally distributes drive torque to the front and rear wheels.
Ensures optimal start-off performance during a start-off, based on
information provided by various sensors.
Suppresses the tight corner braking phenomenon* during low-speed
cornering.
Reduces the amount of torque distribution to the rear wheels and
improves fuel economy when the system judges that the vehicle is
traveling steadily.
Disengages the 4WD during braking deceleration.
LOCKON
Distributes the maximum torque limit to the rear wheels.
Distributes the maximum torque limit to the rear wheels during
start-off.
Distributes optimal torque during low-speed cornering.
Disengages the 4WD during braking deceleration.
Disengages the LOCK mode and transfers to the AUTO mode when
the vehicle speed exceeds 40 km / h (25 mph).
*: Tight corner braking phenomenon: a condition in which the brakes are applied due to a rotational difference
between the front and rear wheels, such as during low-speed cornering in the 4WD mode.
The 4WD ECU effects cooperative control with the skid control ECU, in order to control the drive torque
distribution to the front and rear wheels in accordance with information received from the skid control
ECU. These controls ensure a smooth acceleration and driving stability.

CHASSIS - 4WD SYSTEM
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Electric Control Coupling
4WD ECU
Four-wheel Drive
Lock Switch
4WD LOCK
Indicator Light
4WD Warning
LightECM
Skid Control ECU
Main Body ECU
Ya w R a t e &
Deceleration Sensor
Steering Angle
SensorThrottle Position Sensor
Crankshaft Position Sensor
Park / Neutral Position
Switch
Speed Sensors
Stop Light Switch
Ambient Temperature
Sensor
Parking Brake Switch
CANH,
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2. System Diagram

CHASSIS - 4WD SYSTEM
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Skid Control ECU
Electric Control Coupling
ECM Ambient Temperature
Sensor
Main Body ECUSteering Angle
Sensor
Four-wheel Drive
Lock Switch
4WD ECU
Parking Brake
Switch Stop Light Switch
Yaw Rate & Deceleration
Sensor DLC3 CH-68
3. Layout of Main Components

CHASSIS - 4WD SYSTEMCH-69
4. Function of Main Components
ComponentFunction
Combination
4WD LOCK
Indicator LightIlluminates to inform the driver of the 4WD LOCK mode control.Combination
Meter4WD
Warning LightIlluminates to warn the driver of a malfunction in the 4WD system.
Speed Sensor (4)Detects the wheel speed of each 4 wheel.
Steering Angle SensorDetects the direction and angle of the steering wheel.
Yaw Rate & Deceleration SensorDetects the vehicle’s longitudinal and lateral acceleration.
Crankshaft Position SensorDetects the engine speed and outputs it to the ECM.
Accelerator Pedal Position SensorDetects the accelerator pedal position and outputs it to the ECM.
Throttle Position SensorDetects the throttle valve position and outputs it to the ECM.
Park / Neutral Position SwitchDetects the neutral position of the transaxle and outputs it to the
ECM.
Stop Light SwitchDetects the brake pedal depressing signal.
Parking Brake SwitchDetects when the parking brake lever is pulled up.
Four-wheel Drive Lock SwitchSwitches between the AUTO and LOCK modes.
4WD ECU
Controls the amperage that is applied to the electromagnetic
solenoid of the electric control coupling based on the signals
provided by the sensors in order to optimally distribute drive torque
in accordance with driving conditions.
ECMOutputs signals such as the shift position signal, throttle position
signal, and crankshaft position signal to the 4WD ECU.
Skid Control ECUOutputs signals such as the vehicle speed signal and deceleration
signal to the 4WD ECU.
Electric Control CouplingDistributes drive torque in accordance with the amperage applied
by the 4WD ECU.

CHASSIS - 4WD SYSTEM
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Torque Distribution
to Rear WheelsTorque Distribution
to Rear Wheels
Straightline Driving Low-Speed Cornering
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Torque Distribution
to Rear WheelsTorque Distribution
to Rear Wheels
Steady Driving Straightline Acceleration
NOTICE
In the LOCK mode after the four-wheel drive lock switch is pressed, the system starts control upon
judging that the vehicle is operating in a stable manner. During this judgment, the 4WD LOCK
indicator light blinks.
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5. System Operation
Auto Mode
1) Starting Off
The system ensures start-off performance by optimally distributing the entire drive torque, which is
transmitted by the engine, to the front and rear wheels.
To prevent the tight corner braking phenomenon from occurring during low-speed cornering, the
system reduces the amount of torque distribution to the rear wheels.
2) Normal Driving
During normal driving, when the system judges that the vehicle is traveling steadily, it reduces the
amount of torque distribution to the rear wheels. This allows the vehicle to operate in conditions
similar to front-wheel-drive, which improves fuel economy.
To ensure excellent acceleration performance during straightline acceleration and excellent driving
stability during cornering, the system controls the amount of torque distribution to the rear wheels.
Lock Mode
When the vehicle is in a situation that poses difficulty for it to pull itself out, such as sand, the driver can
switch to LOCK mode by operating the four-wheel drive lock switch. Thus, this mode effects optimal
control in accordance with the driving conditions and transmits as much drive torque as possible to the rear
wheels, in a mode that is similar to the locked 4WD mode.