2006 Lexus GS430 steering

STARTING AND DRIVING
424
ADAPTIVE VARIABLE SUSPENSIONSYSTEM (GS430 only)
G31041
 1Sport position 2Normal position
The adaptive variable suspension system controls the
suspension according to the road and driving conditions.
Selecting an optimum driving mode allows good vehicle
posture and steering wheel operation in conjunction with
variable gear ratio steering system and electric power
steering system.
Sport mode: Suitable for sporty type driving, such as on
winding mountain roads and high speed driving.
Normal mode: Suitable for ordinary driving.
To turn on the sport mode, push the selector switch on the
“SPORT” side. The indicator comes on in the instrument
cluster.
To change to the normal mode, push the switch to the “NORM”
side.
TRACTION CONTROL SYSTEM
The traction control system automatically helps prevent
the spinning of drive wheels when the vehicle is started or
accelerated on slippery road surfaces.
When the engine switch is selected in “IG −ON” mode, the
system automatically turns on.
CAUTION
Under certain slippery road conditions, full traction of
the vehicle and power against drive wheels cannot be
maintained, even though the traction control system is
in operation. Do not drive the vehicle under any speed
or maneuvering conditions which may cause the
vehicle to lose traction control. In situations where the
road surface is covered with ice or snow, your vehicle
should be fitted with snow tires or tire chains. Always
drive at an appropriate and cautious speed for the
present road conditions.

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427
VEHICLE STABILITY CONTROLSYSTEM
The vehicle stability control system helps provide
comprehensive control of the systems such as antilock
brake system, traction control, engine control, etc. This
system automatically controls the brakes and engine to
help prevent the vehicle from skidding when cornering on
a slippery road surface or operating steering wheel
abruptly.
The vehicle stability control system is activated when the
vehicle speed is about more than 15 km/h (9 mph).
You may hear a sound in the engine compartment for a few
seconds just after the vehicle begins to move. This means that
the system is in the self− check mode, but does not indicate a
malfunction.
CAUTION
 Do not rely excessively on the vehicle stability
control system. Even if the vehicle stability control
system is operating, you must always drive carefully
and attentively to avoid serious injury. Reckless
driving will result in an accident. If the slip indicator
light blinks, sounding an alarm, special care should
be taken while driving.
 Only use tires of specified size. The size,
manufacturer, brand and tread pattern for all 4 tires
should be the same. If you use the tires other than
specified, or different type or size, the vehicle
stability control system may not function correctly.
When replacing the tires or wheels, contact your
Lexus dealer.
 In situations where the road surface is covered with
ice or snow, your vehicle should be fitted with snow
tires or tire chains.

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VARIABLE GEAR RATIO STEERING SYSTEM (GS430 only)
The variable gear ratio steering system adjusts the wheel
turning angle depending on the vehicle speed and how
much you turn the steering wheel.
The vehicle wheel turning angle will be changed with a smaller
degree of wheel maneuvering when you are driving at very low
speed such as when putting your vehicle into a garage.
When you start or stop the engine, you may hear a small noise
and the steering wheel may move slightly. This is caused when
the system starts or stops, and does not indicate a malfunction.
In the following cases, to prevent the system from overheating,
the system could be temporarily deactivated with the change
in the center position of the steering wheel. This is not a
malfunction. After the cause of the problem is eliminated, the
system will return to normal automatically after a few minutes.
 If you continue maneuvering the steering wheel when the
vehicle is stopped or running at very low speed
 If you continue driving holding the steering wheel to the
extreme right or left
 If you maneuver the steering wheel immediately after
starting the engine at less than about −30C (− 22F) While the system is not functioning, a larger degree of wheel
maneuvering is needed during driving at low speed. If the
center position of the steering wheel is changed frequently,
have your vehicle inspected at your Lexus dealer.CAUTION
Take due care especially when driving at low speed as
the vehicle changes direction in greater proportion to
the steering wheel maneuvering.
NOTICE
Do not disconnect the battery with the steering wheel
turned, or the center position of the steering wheel
could be slightly and temporarily changed. However,
after driving for a short while, the system will return to
normal
and the center position of the steering wheel will
be in the appropriate position.
If you disconnect and reconnect the battery terminal, the
system is reset temporarily. However, it is no problem to drive.
Drive for a short while, the system will be set automatically and
return to normal.

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Variable gear ratio steering system failure
warning
G31044
If there is any malfunction in the system, the above message
appears and the master warning light comes on.
If the warning message and light come on while driving, the
system is not working. Although conventional steering
operates when maneuvered, a larger degree of wheel
maneuvering (than at the time when the system is functioning
properly) is needed when driving at low speed. At this time, the
center position of the steering wheel could be changed.
Although it is no problem to continue driving, have your vehicle
repaired at your Lexus dealer.
VEHICLE DYNAMICS
INTEGRATED MANAGEMENT (GS430 only)
Vehicle Dynamics Integrated Management (VDIM) helps
manage control for vehicle stability control system,
antilock brake system, brake assist system, traction
control system, engine output control, hillstart assist
control system and also manages variable gear ratio
steering system and electric power steering system.
In order to control sudden steering wheel operation and
the sideslip on slippery road surfaces, this system
provides excellent vehicle stability by automatically
controlling the brake, engine output and front wheel
angle.
The state of the tires will affect the performance of the vehicle
dynamics integrated management system. Be sure to check
the following:
 Are tires of specified size installed?
 Are tires of identical type installed?
 Do the tires have stipulated tire pressure?
 Are the tires worn?
A problem with the tires or modified suspension systems will
have an adverse effect on the system and may cause a
malfunction, so be careful.

STARTING AND DRIVING
434Any of the following conditions may occur, but does not
indicate a malfunction:

The brake system warning light (red) may stay on for about
60 seconds after the engine is started. It is normal if the light
turns off after a while.
 Depressing the brake pedal repeatedly may turn on the
brake system warning light (red). It is normal if the light goes
out after a few seconds.
 You may hear a small sound in the engine compartment
after the engine is started or the brake pedal is depressed
repeatedly. This is a pump pulsating sound of the brake
system.
CAUTION
Do not pump the brake pedal if the engine stalls.
Each push on the pedal uses up your reserved brake
fluid pressure.
 Even if the power assist is completely lost, the brakes
will still work. But you will have to push the pedal
hard, much harder than normal. And your braking
distance will increase.
Brake booster (GS300)
The brake booster uses engine vacuum to power −assist the
brakes. If the engine should quit while you are driving, you can
bring the vehicle to a stop with normal pedal pressure. There
is enough reserved vacuum for one or two stops but no more!
CAUTION
 Do not pump the brake pedal if the engine stalls.
Each push on the pedal uses up your reserved
vacuum.
 Even if the power assist is completely lost, the brakes
will still work. But you will have to push the pedal
hard, much harder than normal. And your braking
distance will increase.
Antilock brake system
The antilock brake system is designed to automatically
help prevent lockup of the wheels during a sudden
braking or braking on slippery road surfaces. This assists
in providing directional stability and steering
performance of the vehicle under these circumstances.
Effective way to press the ABS brake pedal: When the
anti−lock brake system function is in action, you may feel the
brake pedal pulsating and hear a noise. In this situation, to
let the anti−lock brake system work for you, just hold the
brake pedal down more firmly. Do not pump the brake in a
panic stop. This will result in reduced braking performance.

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The anti
−lock brake system becomes operative after the
vehicle has accelerated to a speed in excess of approximately
10 km/h (6 mph). It stops operating when the vehicle
decelerates to a speed below approximately 5 km/h (3 mph).
Depressing the brake pedal on slippery road surfaces such as
on a manhole cover, a steel plate at a construction site, joints
in a bridge, etc. on a rainy day tends to activate the anti −lock
brake system.
You may hear a click or motor sound in the engine
compartment for a few seconds when the engine is started or
just after the vehicle begins to move. This means that the
anti−lock brake system is in the self− check mode, and does not
indicate a malfunction.
When the antilock brake system is activated, the
following conditions may occur. They do not indicate a
malfunction of the system:
 You may hear the anti− lock brake system operating and feel
the brake pedal pulsating and the vibrations of the vehicle
body and steering wheel. You may also hear the motor
sound in the engine compartment even after the vehicle is
stopped.
 At the end of the anti−lock brake system activation, the
brake pedal may move a little forward.
CAUTION
Do not overestimate the antilock brake system:
Although the antilock brake system assists in
providing vehicle control, it is still important to drive
with all due care and maintain a moderate speed and
safe distance from the vehicle in front of you, because
there are limits to the vehicle stability and effectiveness
of steering wheel operation even with the antilock
brake system on.
If tire grip performance exceeds its capability, or if
hydroplaning occurs during high speed driving in the
rain, the antilock brake system does not provide
vehicle control.
Antilock brake system is not designed to shorten the
stopping distance: Always drive at a moderate speed
and maintain a safe distance from the vehicle in front of
you. Compared with vehicles without an antilock
brake system, your vehicle may require a longer
stopping distance in the following cases:
 Driving on rough, gravel or snowcovered roads.
 Driving with tire chains installed.
 Driving over the st eps such as the joints on the road.
 Driving on roads where the road surface is pitted or
has other differences in surface height.

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BRAKE PAD WEAR LIMITINDICATORS
G31006
The brake pad wear limit indicators on your disc brakes
give a warning noise when the brake pads are worn to the
extent that replacement is required.
If you hear a squealing or scraping noise while driving, have
the brake pads checked and replaced by your Lexus dealer as
soon as possible. Expensive rotor damage can result if the
pads are not replaced when needed.
GS430 front brake only—
The high brake performance is achieved by proper wear of
brake pads and discs. As a result, the brake discs may wear
earlier than the ones on the conventional brake system.
When brake pads are replaced, brake disc thickness is
required to be measured.
It is dangerous to continue driving when brake pads and discs
have exceeded the wear limit.
ELECTRIC POWER STEERING SYSTEM
The electric power steering system, using an electric
motor, assists the turning of the steering wheel.
In the following cases, you may feel the steering becomes
heavy. However, the electric power steering system
warning light does not come on. (Because it is not a
malfunction.)
When maneuvering or turning frequently over a long time, the
power steering effect will be reduced to prevent the system
from overheating. A void turning the steering wheel, or stop the
vehicle. The system will become cool in about 10 minutes.
NOTICE
Frequent maneuvering and turning over a long time may
cause damage to the system in which the mechanism
prevents overheating of the electric power steering
system.
When the battery is discharged, check the battery’s condition.
If necessary, recharge or replace the battery. For details, see
“Checking battery condition” on page 581.

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G31040
Electric power steering system warning light
The light comes on when the engine switch is selected in
“IG−ON” mode. If the electric power steering system works
properly, the light turns off after a few seconds. If the system
has malfunctions, the light comes on again.
If the following conditions occur, this indicates a
malfunction somewhere in the components monitored by
the warning light system. Contact your Lexus dealer as
soon as possible to service the vehicle.
 The light does not come on when the engine switch is
selected in “IG −ON” mode or remains on.
 The light stays on while you are driving.
CAUTION
If the electric power steering system warning light
comes on, take your vehicle to your Lexus dealer as
soon as possible. In this case, more effort is required
for the steering wheel to turn than usual. Drive your
vehicle while firmly gripping the steering wheel.