2004 Lexus GX470 Audio System / LEXUS 2004 GX470 FROM NOV. 2003 THROUGH DEC. 2003 PROD. OWNER'S MANUAL (OM60A74U)

STARTING AND DRIVING
408
DOWNHILL ASSIST CONTROL
SYSTEM
The downhill assist control system is a system that
assists the deceleration of the engine brake when you
drive down a steep hill. When you are driving down a hill
with the four-wheel drive control lever in the Lº position,
push the DACº switch to limit the vehicle's acceleration.
If the vehicle is traveling at a speed of 25 km/h (15 mph) or
less, you can descend at a constant speed.
CAUTION
Do not rely excessively on the downhill assist control
system. It may not be able to maintain a low speed over
road surfaces or off-road surfaces on which sliding can
easily occur, such as extremely steep slopes or icy or
muddy roads.
Turning on the system
1. Shift the four-wheel drive control lever to the Lº
position.
The system will not operate if the four-wheel drive control lever
is in the Hº position.
2. In order to make full use of the engine brake, putting the
transmission in Lº or 2º is recommended.
The system will operate even if the transmission selector lever
is in Dº, 4º, 3º or Nº. However, when it is in Lº or 2º the
engine brake can also be utilized enabling the system to
operate more effectively.
3. Push the DACº switch to turn the system on. The
downhill assist control system indicator light on the
instrument panel will come on.
If the downhill assist control system indicator light flashes, the
transmission selector lever may be in Nº or four-wheel drive
control lever may be in the Hº position.

STARTING AND DRIVING
409 If the indicator light does not come on when the switch is
pushed, contact your Lexus dealer.

Slip indicator light
With the vehicle traveling at a speed of 25 km/h (15 mph) or
less, release your foot from the accelerator or brake pedal to
activate the system. The vehicle will descend the hill at a low
speed. While the system is operating, the slip indicator light on
the instrument panel will flash and the stop lights and high
mounted stoplight will be lit.
If you push the DACº switch to turn the system off while it is
in operation, the system will stop operating gradually. The
downhill assist control system indicator light will flash to alert
the driver. To continue driving at a low speed, push the DACº
switch to turn the system on.
The slip indicator light and downhill assist control system
indicator light come on for a few seconds when the ignition key
is turned to ONº. If any of the indicator lights does not come
on when the ignition is turned on, contact your Lexus dealer.If the system is used frequently, the brake actuator
temperature may become too high and a buzzer will sound
intermittently.
If this happens, the downhill assist control system indicator
light will flash and a buzzer will sound intermittently. When the
temperature of the brake actuator goes down, the system will
begin to operate again. Until it restarts, the active traction
control system and hill-start assist control system will not
operate; however, the conventional brake can be operated.

STARTING AND DRIVING
410
VSC TRACº warning light
If there is any abnormality in the system, the VSC TRACº
warning light will come on. When the DACº switch is
pushed, the downhill assist control system indicator light
also flash.
If the VSC TRACº warning light comes on, there may be an
abnormality in any of the following systems in addition to the
downhill assist control system.
Hill-start assist control system
Active traction control system
Vehicle stability control system
When the system is normal and the ignition key is turned to
ONº, the warning light will come on and will go off after a few
seconds. It is not a malfunction that the warning light may stay
on for 60 seconds after the ignition key is turned to the ONº
position.Depressing the brake pedal repeatedly may turn on the light.
It is normal if it goes out after a few seconds.
The brake actuator temperature increases during continuous
operation of the above mentioned system on such as slippery
roads. If the brake actuator temperature becomes too high
while any of the systems is operating, a buzzer will start to
sound intermittently to indicate that the downhill assist control
system can no longer operate. In this case, stop your vehicle
immediately at a safe place.
If the system continues to operate, the buzzer sound changes
from intermittent to continuous. (The continuous buzzer
sounds for about 3 seconds.) At this time, the VSC TRACº
warning light will come on and the downhill assist control
system stops operating temporarily in order to protect the
brake actuator. (Although the downhill assist control system
does not operate, it is no problem to continue your driving.) The
system will be automatically restored after a short time and the
VSC TRACº warning light goes out.
If the warning light comes on while driving, the system does not
work. However, as normal braking operates when being
applied, it is no problem to continue your driving.
In the following cases, contact your Lexus dealer:
The warning light does not come on after the ignition key is
turned to ONº.
The warning light remains on after the ignition key is turned
to ONº.
The warning light comes on while driving.

STARTING AND DRIVING
411
HILL-ST ART ASSIST CONTROL
SYSTEM
The hill-start 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 prevent the vehicle
from rolling backward in the interval while you move your
foot from the brake pedal to the accelerator pedal.
CAUTION
Do not rely excessively on the hill-start assist control
system. The vehicle may not be able to start
smoothly on road surfaces or off-road surfaces such
as extremely steep slopes or icy roads, on which
sliding can occur very easily.
Do not use the hill-start assist control system to stop
the vehicle. This system is not designed as a function
for stopping the vehicle on a uphill slope.
The hill-start assist control system will operate for 5
seconds maximally when all of the following conditions
apply.
When the transmission is in any of positions Dº, 4º,
3º, 2º or Lº
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 transmission is in Pº or Nº
it will not operate. It will not operate either if the vehicle starts
to move in reverse on a slope with the transmission in the Rº.

Slip indicator light
When the hill-start assist control system is operating, the slip
indicator light flashes and an alarm sounds intermittently. At
the same time, the stop lamps and high mounted stoplight are
lit.

STARTING AND DRIVING
412The slip indicator light comes on for a few seconds when the
ignition key is turned to ONº. If the indicator light does not
come on when the ignition is turned on, contact your Lexus
dealer.
Keep in mind the following 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 buzzer will
sound at more frequent intervals and the system will
gradually stop operating.
The hill-start assist control system is not designed as a
function for stopping the vehicle on a uphill slope. When
stopping the vehicle, be sure to depress the brake pedal.
If the system is used frequently, the brake actuator
temperature may become too high and a buzzer will sound
intermittently.
In this case, a buzzer will sound intermittently. When the
temperature of the brake actuator goes down, the system will
begin to operate again. Until it restarts, the active traction
control system and downhill assist control system will not
operate; however, the conventional brake can be operated.
VSC TRACº warning light
If there is any abnormality in the system, the VSC TRACº
warning light will come on.
If the system malfunctions, the VSC TRACº warning light will
come on.
If the VSC TRACº warning light comes on, there may be an
abnormality in any of the following systems in addition to the
hill-start assist control system.
Downhill assist control system
Active traction control system
Vehicle stability control system
When the system is normal and the ignition key is turned to
ONº, the warning light will come on and will go off after a few
seconds. It is not a malfunction that the warning light may stay
on for 60 seconds after the ignition key is turned to the ONº
position.

STARTING AND DRIVING
413 Depressing the brake pedal repeatedly may turn on the light.
It is normal if it goes out after a few seconds.
The brake actuator temperature increases during continuous
operation of the above mentioned system on such as slippery
roads. If the brake actuator temperature becomes too high
while any of the systems is operating, a buzzer will start to
sound intermittently to indicate that the hill-start assist control
system can no longer operate. In this case, stop your vehicle
immediately at a safe place.
If the system continues to operate, the buzzer sound changes
from intermittent to continuous. (The continuous buzzer
sounds for about 3 seconds.) At this time, the VSC TRACº
warning light will come on and the hill-start assist control
system stops operating temporarily in order to protect the
brake actuator. (Although the hill-start assist control system
does not operate, it is no problem to continue your driving.) The
system will be automatically restored after a short time and the
VSC TRACº warning light goes out.
If the warning light comes on while driving, the system does not
work. However, as normal braking operates when being
applied, it is no problem to continue your driving.
In the following cases, contact your Lexus dealer:
The warning light does not come on after the ignition key is
turned to ONº.
The warning light remains on after the ignition key is turned
to ONº.
The warning light comes on while driving.
BRAKE SYSTEM
This brake system has 2 independent hydraulic circuits. If
either circuit 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 may come on.
CAUTION
Do not drive your vehicle with only a single brake
system. Have your brakes fixed immediately.
Brake booster
The brake booster uses brake fluid pressurized by the pump
to power-assist the brakes. If the brake booster fails during
driving, the brake system warning light comes on and buzzer
sounds continuously. In this case, the brakes may not work
properly. If they do not work well, depress the brake pedal
firmly. If the brake system warning light comes on, immediately
stop your vehicle and contact your Lexus dealer.
The brake system warning light may stay on for about 60
seconds after the ignition key is turned to the ONº position. It
is normal if the light turns off after a while.
Depressing the brake pedal repeatedly may turn on the brake
system warning light and buzzer. It is normal if the light goes
out and the buzzer stops sounding after a few seconds.

STARTING AND DRIVING
414You 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, and it is not a malfunction.
CAUTION
Do not pump the brake pedal if the engine stalls.
Each push on the pedal uses up your brake fluid
pressure reserve.
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.
Anti-lock brake system
The anti-lock brake system is designed to automatically
help prevent lock-up of the wheels during a sudden brake
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.
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 anti-lock 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 to the forward.

STARTING AND DRIVING
415
CAUTION
Do not overestimate the anti-lock brake system:
Although the anti-lock 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 anti-lock
brake system on.
If tire grip performance exceeds its capability, or if
hydroplaning occurs during high speed driving in the
rain, the anti-lock brake system does not provide
vehicle control.
Anti-lock 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 anti-lock
brake system, your vehicle may require a longer
stopping distance in the following cases:
Driving on rough, gravel or snow-covered roads.
Driving with tire chains installed.
Driving over the steps such as the joints on the road.
Driving on roads where the road surface is pitted or
has other differences in surface height.
Install all 4 tires of specified size at appropriate
pressure: The anti-lock 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.