Toyota ACA33 Series, Electrical Wiring Diagram

Page: 261 / 434

260
RAV4 (EM03T0U)
ABS, TRAC, VSC, Downhill Assist Control, Hill–Start Assist Control and Auto LSD
1. ABS Operation
If the brake pedal is depressed suddenly, the ABS controls the hydraulic pressure of the wheel cylinders for all the four
wheels to automatically avoid wheel locking and ensure the directional and steering stability of the vehicle. If the brake pedal
is depressed suddenly, the skid control ECU controls the solenoids in the actuators using the signals from the sensors to
move the brake fluid to the reservoir in order to release the braking pressure applied to the wheel cylinder. If the skid control
ECU detects that the fluid pressure in the wheel cylinder is insufficient, the ECU controls the solenoids in the actuators to
increase the braking pressure.
2. Traction Control Operation
The traction control system controls the engine torque, the hydraulic pressure of the driving wheel cylinders, slipping of the
wheels which may occur at start or acceleration of the vehicle, to ensure an optimal driving power and vehicle stability
corresponding to the road conditions.
3. VSC Operation
Unexpected road conditions, vehicle speed, emergency situation, and any other external factors may cause large under– or
over–steering of the vehicle. If this occurs, the VSC system automatically controls the engine power and wheel brakes to
reduce the under– or over–steering.
To reduce large over–steering :
If the VSC system determines that the over–steering is large, it activates the brakes for the outer turning wheels depending
on the degree of the over–steering to produce the moment toward the outside of the vehicle and reduce the over–steering.
To reduce large under–steering :
If the VSC system determines that the under–steering is large, it controls the engine power and activates the rear wheel
brakes to reduce the under–steering.
4. Fail Safe Function
If an error occurs in the skid control ECU, sensor signals, and/or actuators, the skid control ECU inhibits the brake actuator
control and inputs the error signal to the engine control module. According to the error signal, the brake actuator turns off the
solenoid and the engine control module rejects any electronically controlled throttle open request from the VSC system. As a
result, the vehicle functions regardless of the ABS, TRAC, and VSC systems.
5. Downhill Assist Control Operation
The downhill assist control operation controls braking action of each wheel to help prevent out–of–balance vehicle posture
when descending a steep hill or traveling at a speed exceeding the threshold of wheel gripping capability. When the downhill
assist control is in operation, the brake system control vehicles speed within the range of 5 to 7 km/h.
6. Hill–Start Assist Control Operation
When starting on a steep hill for ascending, the hill–start support control automatically puts the brake on momentarily – from
the moment when the driver releases his foot from the brake pedal until he steps on the accelerator pedal – to help the driver
start the vehicle safely and smoothly.
Please bear in mind, however, that it activates the brake system for only 3 seconds.
7. Auto LSD
Auto LSD fulfills the function of LSD (Limited Slip Differential) by using the system of TRAC. It control to focus on ’getting
out’, which ensures to recover from run–off condition and to take off on roads with much travel resistance such as sand.
: Parts Location
Code See Page Code See Page Code See Page
A2 56 A41 52 (2AZ–FE) E69 55
A3 56
A42
50 (2GR–FE) E70 55
A19
50 (2GR–FE)
A42
52 (2AZ–FE) K6 59
A19
52 (2AZ–FE) E11 54 K22 59
A35 56 E13 54 K23 59
A36 56 E19 54 V1 61
A37 56 E31 54 W1 61
A38 56 E51 55
A41 50 (2GR–FE) E68 55
System Outline