CHASSIS - 4WD SYSTEM
01NCH38Y
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.
CHASSIS - 4WD SYSTEM
Service Tip
When the 4WD ECU judges that the vehicle has become stable, it cancels the stopping of the 4WD
control and transfers to AUTO control. If the 4WD warning light blinks, take the following actions
without turning the engine OFF:
Drop the vehicle speed until the light goes out
Stop the vehicle and stay there until the light goes out
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6. Diagnosis
When the 4WD ECU detects a malfunction, the 4WD ECU makes a diagnosis and memorizes the failed
section. Furthermore, the 4WD warning light in the combination meter illuminates to inform the driver.
At the same time, the DTCs (Diagnosis Trouble Codes) are stored in memory. The DTCs can be read by
connecting a hand-held tester, or by connecting the SST (09843-18040) to the TC and CG terminals of
DLC3 and observing the blinks of the 4WD warning light.
For details of the DTCs that are stored in 4WD ECU memory, see the 2006 RAV4 Repair Manual (Pub. No.
RM01M1U).
7. Fail-safe
When there is a possibility of causing damage to the drive system due to a malfunction in the 4WD system
or rough driving, the system illuminates or blinks the 4WD warning light to inform the driver, stops the 4WD
controls, and enables the vehicle to operate in the front-wheel-drive mode.
Malfunction
4WD Warning Light
4WD System MalfunctionIlluminate
Rough driving in 4WDPre-warning for stopping 4WD controlSlow blinkingRough driving in 4WDStopping 4WD controlFast blinking