ABS Antilock Brake System
A/C Air Conditioner
assy assembly
ECT Electronic Controlled Transmission
ECU Electronic Control Unit
e.g. Exempli Gratia (for Example)
Ex. Except
4WD Four Wheel Drive Vehicles
in. inch
LH Left-hand
LHD Left-hand Drive
MIG Metal Inert Gas
M/Y Model Year
PPS Progressive Power Steering
RH Right-hand
RHD Right-hand Drive
SRS Supplemental Restraint System
SSM Special Service Materials
w/ with
w/o without
5. ECU (ELECTRONIC CONTROL UNIT)
Many ECUs are mounted in this vehicle.
Take the following precautions during body repair to prevent damage to the ECUs.
Before starting electric welding operations, disconnect the negative (-) terminal cable from the battery.
When the negative (-) terminal cable is disconnected from the battery, memory of the clock and audio
systems will be cancelled. So before starting work, make a record of the contents memorized by each
memory system. Then when work is finished, reset the clock and audio systems as before.
When the vehicle has tilt and telescopic steering, power seat and outside rear view mirror, which are all
equipped with memory function, it is not possible to make a record of the memory contents. So when the
operation is finished, it will be necessary to explain this fact to the customer, and request the customer to
adjust the features and reset the memory.
Do not expose the ECUs to ambient temperatures above 80°C (176°F).
NOTICE: If it is possible the ambient temperature may reach 80° (176°F) or more, remove the ECUs
from the vehicle before starting work.
Be careful not to drop the ECUs and not to apply physical shocks to them.
ABBREVIATIONS USED IN THIS MANUAL
For convenience, the following abbreviations are used in this
manual.
INTRODUCTIONIN-9
2004 LAND CRUISER (EWD548U)
234VSC
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 ABS & BA & TRAC & VSC 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
ABS & BA & TRAC & VSC 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.
VSC indicator light
If an error occurs in the VSC system, the VSC indicator lights up to warn the driver.
4. Traction Mode and VSC Function
When the center differential of the transfer is locked, the VSC function is turned off. At this time, the VSC OFF indicator light
in the combination meter will come on, and informs the driver that the VSC function is OFF.
5. Mutual System Control
To efficiently operate the VSC system at its optimal level, the VSC system and other control systems are mutually controlled
while the VSC system is being operated.
Engine throttle control
The engine power does not interfere with the VSC brake control by controlling the opening of the throttle and reducing the
engine output.
Engine control and electronically controlled transmission control
The strong braking force does not interfere with the braking force control of the VSC system by turning off the accel. and
reducing changes in the driving torque at shift-down.
VSC system operation indication
The slip indicator light flashes and the buzzer sounds intermittently to warn the driver that the current road is slippery, while
the VSC system is being operated.
6. Fail Safe Function
If an error occurs in the ABS & BA & TRAC & VSC ECU, sensor signals, and/or actuators, the ABS & BA & TRAC & VSC
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 without the ABS, BA, TRAC, and VSC systems.
System Outline
