Lexus GS430 2006 Scheduled Maintenance Guide / LEXUS 2006 GS430/GS300 FROM JAN. 2006 PROD. OWNER'S MANUAL (OM30786U)

STARTING AND DRIVING
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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428
G31038
Slip indicator light
If the vehicle is going to skid during driving, the slip indicator
light blinks and an alarm sounds intermittently. Special care
should be taken while driving.
GS430—The slip indicator light comes on when the engine
switch is selected in “IG− ON” mode. The light goes off when
the engine is started.
GS300—The slip indicator light comes on for a few seconds
when the engine switch is selected in “IG −ON” mode.
If the indicator light does not come on when the engine switch
is selected in “IG −ON” mode, contact your Lexus dealer.
Vehicle stability control failure warning
G31039
 1
GS430 2GS300
If the vehicle stability control system malfunctions, the
slip indicator light (twowheel drive models only) and
brake system warning light (yellow) come on. At this time,
the above message appears. (GS430 only—In some
cases, the multiinformation display shows either
“CHECK VSC” or “CHECK ECB*” only.)
*: Electronically Controlled Brake System
If the message appears, the vehicle stability control system,
traction control system and hill −start assist control system do
not work. Although it is no problem to continue driving, have
your vehicle checked by your Lexus dealer as soon as
possible.

STARTING AND DRIVING
429
HILLSTART ASSIST CONTROLSYSTEM
The hillstart assist control system assists you in starting
to move up a steep or slippery hill. When you start to move
up the hill slope, the system helps to reduce the vehicle’s
rolling backward distance while you move your foot from
the brake pedal to the accelerator pedal.
CAUTION
 Do not rely excessively on the hillstart assist control
system. The vehicle may not be able to start
smoothly on road surfaces or offroad surfaces such
as extremely steep slopes or icy roads, on which
sliding can occur very easily.
 Do not use the hillstart assist control system to stop
the vehicle. This system is not designed for stopping
the vehicle on an uphill slope.
The hillstart assist control system will operate for 5
seconds maximally when all of the following conditions
apply.
When the selector lever is in “D” or “S” position
 When the brake pedal is not depressed
The system is designed to operate when the vehicle is starting
on an uphill slope; therefore, if the selector lever is in “P” or “\
N”,
it will not operate. It will not operate either if the vehicle starts
to move in reverse on a slope with the selector lever in “R”.
When the hill−start assist control system is operating, you may
hear a sound. This indicates the hill−start assist control is
operating normally and does not indicate a malfunction.
G31038
 Slip indicator light
When the hill −start assist control system is operating, the slip
indicator light flashes. At the same time, the stop lights and
high mounted stoplight are lit.

STARTING AND DRIVING
430GS430—The slip indicator light comes on when the engine
switch is selected in “IG−
ON” mode. The light goes off when
the engine is started.
GS300—The slip indicator light comes on for a few seconds
when the engine switch is selected in “IG −ON” mode.
If the indicator light does not come on when the engine switch
is selected in “IG −ON” mode, contact your Lexus dealer.
Keep the following in mind when driving:
 The hill −start assist control system operates for 5 seconds
maximally. If both the brake and accelerator pedals remain
undepressed for longer than 5 seconds, the system will
gradually stop operating.
 The hill− start assist control system is not designed for
stopping the vehicle on an uphill slope. When stopping the
vehicle, be sure to depress the brake pedal.
Hillstart assist control system failure
warning
G31039
 1 GS430 2GS300
If the hillstart assist control system malfunctions, the
slip indicator light (twowheel drive models only) and
brake system warning light (yellow) come on. At this time,
the above message appears. (GS430 only—In some
cases, the multiinformation display shows either
“CHECK VSC” or “CHECK ECB*” only.)
*: Electronically Controlled Brake System
If the message appears, the hill−start assist control system,
vehicle stability control system and traction control system do
not work. Although it is no problem to continue driving, have
your vehicle checked by your Lexus dealer as soon as
possible.

STARTING AND DRIVING
431
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.

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When the slip indicator light comes on, and the message
“CHECK ECB*” appears
on the multi−information display, the
vehicle dynamics integrated management does not operate.
Have your vehicle checked by your Lexus dealer as soon as
possible.
*: Electronically Controlled Brake System
In addition, when the master warning light comes on, and the
message “CHECK VGRS” or “CHECK P/S” appears on the
multi−information display, the system will not be temporarily
functioning. Although it is no problem in driving as usual, have
your vehicle checked by your Lexus dealer as soon as
possible.
CAUTION
Do not overestimate the vehicle dynamics integrated
management. Even when this management is
functional, there is a limit to vehicle stability, and
irresponsible driving may lead to an accident. When
driving, you should always pay attention to your speed
and keep a safe distance between your vehicle and the
vehicle in front.
BRAKE SYSTEM
GS430:
This brake system has 3 independent hydraulic circuits. If any
circuits should fail, the other will still work. However, the pedal
will be harder to press, and your stopping distance will
increase. Also, the brake system warning light (red) may come
on.
GS300:
The tandem master cylinder brake system is a hydraulic
system with two separate sub −systems. If either sub −system
should fail, the other will still work. However, the pedal will be
harder to press, and your stopping distance will increase. Also,
the brake system warning light (red) may come on.
CAUTION
Do not drive your vehicle with only a single brake
system. Have your brakes fixed immediately.
Brake actuator (GS430)
The brake actuator uses brake fluid pressurized by the pump
to power −assist the brakes. If the brake actuator fails during
driving, the brake system warning light (red) comes on and the
buzzer sounds continuously. In this case, the brakes may not
work properly. If the brake system warning light comes on,
immediately stop your vehicle and contact your Lexus dealer.

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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Install all 4 tires of specified size at appropriate
pressure: The antilock brake system detects vehicle
speeds using the speed sensors for respective wheels’
turning speeds. The use of tires other than specified
may fail to detect the accurate turning speed resulting
in a longer stopping distance.“ABS” warning light
G31080
 1 U.S.A. 2Canada
GS430—The light comes on when the engine switch is
selected in “IG −ON” mode. If the anti −lock brake system and
the brake assist system work properly, the light turns off in a
few seconds after the engine is started.
GS300—The light comes on for a few seconds when the
engine switch is selected in “IG −ON” mode. It indicates the
anti− lock brake system and the brake assist system work
properly.
If either system malfunctions, the light comes on again.
When the “ABS” warning light is on, the anti− lock brake system
and the brake assist system do not operate, but the brake
system still operates conventionally.