2010 Lexus HS250h Basic Information Before Operation / LEXUS 2010 HS250H OWNERS MANUAL (OM75006U)

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2-4. Using other driving systems
2
When driving
Driving assist systems
To help enhance driving safety and performance, the following systems
operate automatically in response to various driving situations. Be aware,
however, that these systems are supplementary and should not be relied
upon too heavily when operating the vehicle.
■ABS (Anti-lock Brake System)
Helps to prevent wheel lock when the brakes are applied suddenly, or if
the brakes are applied while driving on a slippery road surface
■ Brake assist
Generates an increased level of braking force after the brake pedal is
depressed when the system detects a panic stop situation
■VSC (Vehicle Stability Control)
Helps the driver to control skidding wh en swerving suddenly or turning on
slippery road surfaces
■ TRAC (Traction Control)
Helps to maintain drive power and prevents the drive wheels from spin -
ning when starting the vehicle or
accelerating on slippery roads
■EPS (Electric Power Steering)
Employs an electric motor to reduce the amount of effort needed to turn
the steering wheel
■Enhanced VSC (Enhanced vehicle stability control)
Provides cooperative control of the ABS, TRAC, VSC and EPS. 
Helps to maintain directional stability when swerving on slippery road sur -
faces by controlling steering performance.
■ PCS (Pre-Collision System) (if equipped)
 P. 2 3 3

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2-4. Using other driving systems
When the VSC/TRAC systems are operating
If the vehicle is in danger of slip-
ping or if any of the drive wheels
spins, the slip indicator light flashes
to indicate that the V

SC/TRAC
systems are operating.
A buzzer (intermittent) sounds to
indicate that VSC is operating.
Disabling the TRAC/VSC systems
If the vehicle gets stuck in fresh snow or mud, the TRAC and VSC sys -
tems may reduce power from the hybr id sy
stem to the wheels. You may
need to turn the system off to enable you to rock the vehicle in order to
free it.
■ T
urning off the TRAC system only
To turn the TRAC system off,
quickly pr
ess and release the but -
ton.
A message will be shown on the
multi-information display.
Press the button again to turn the
sy
stem back on.

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2-4. Using other driving systems
2
When driving
■Turning off both TRAC and VSC systems
To turn the TRAC and VSC sys-
tems off, press and hold the button
for mor
e than 3 seconds while the
vehicle is stopped.
A message will be shown on the
multi-information display and
“VSC OFF” indicator will come on.
Press the button again to turn the
sy
stems back on.
■Sounds and vibrations caused by the ABS, brake assist, VSC and TRAC
●A sound may be heard from the engine compartment when the hybrid system is
started, just after the vehicle begins to move, if the brake pedal is depressed
repeatedly, or 1-2 minutes after the hybrid system is stopped. This sound does
not indicate that a malfunction has occurred in any of these systems.
●Any of the following conditions may occur when the above systems are operat -
ing. None of these indicates that a malfunction has occurred.
• Vibrations may be felt through the vehicle body and steering.
• A motor sound may be heard after the vehicle comes to a stop.
• The brake pedal may pulsate slightly after the ABS is activated.
• The brake pedal may move down s lightly af
ter the ABS is activated.
■EPS operation sound
When the steering wheel is operated, a motor soun
d (whirring sound) may be
heard. This does not indicate a malfunction.
■Reactivation of the TRAC /VSC systems
Turning off the hybrid system after turning off the TRAC/VSC systems will automat -
ically reactivate them.
■Reactivation of the TRAC sy stem linked to vehicle speed
When only the TRAC system is turned of
f, the TRAC system will turn on when vehi -
cle speed increases. However, when both TR
AC and VSC systems are turned off,
the systems will not turn on even when vehicle speed increases.

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2-4. Using other driving systems
■Reduced effectiveness of the EPS system
The effectiveness of the EPS system is reduced to prevent the system from over-
heating when there is frequent steering input over an extended period of time. The
steering wheel may feel heavy as a result. Should this occur, refrain from excessive
steering input or stop the vehicle and turn the hybrid system off. The EPS system
should return to normal within 10 minutes.
CAUTION
■The ABS does not operate effectively when
●Tires with inadequate gripping ability are used (such as excessively worn tires on
a snow covered road).
●The vehicle hydroplanes while driving at high speed on wet or slick road.
■Stopping distance when the ABS is operating will exceed that of normal condi-
tions
The ABS is not designed to shorten the vehicle’s stopping dist ance. Always main-
tain a safe distance from the vehicle in front of you in the following situations:
●When driving on dirt, gravel or snow-covered roads
●When driving with tire chains
●When driving over bumps in the road
●When driving over roads with potholes or roads with uneven surfaces
■TRAC may not operate effectively when
Directional control and power may not be ac hievable while driving on slippery road
surfaces, even if the TRAC system is operating. 
Do not drive the vehicle in conditions where stability and power may be lost.
■When the VSC is activated
The slip indicator light flashes and a warning buzzer sounds. Always drive carefully.
Reckless driving may cause an accident. Exercise particular care when the indica-
tor light flashes and a buzzer sounds.
■When the TRAC/VSC systems are turned off
Be especially careful and drive at a speed appropriate to the road conditions. As
these are the systems to ensure vehicle stability and driving force, do not turn the
TRAC/VSC systems off unless necessary.

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2-4. Using other driving systems
2
When driving
CAUTION
■Replacing tires
Make sure that all tires are of the specified size, brand, tread pattern and total load
capacity. In addition, make sure that the tires are inflated to the recommended tire
inflation pressure level.
The ABS and VSC systems will not function correctly if different tires are installed
on the vehicle. 
Contact your Lexus dealer for further info rmation when replacing tires or wheels.
■Handling of tires and the suspension
Using tires with any kind of problem or modifying the suspension will affect the driv-
ing assist systems, and may cause a system to malfunction.

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2-4. Using other driving systems
Hill-start assist control
■Hill-start assist control can be operated when
●The shift position is in a position other than P.
●The parking brake is not applied.
●The accelerator pedal is not depressed.
■Hill-start assist control
●While hill-start assist control is operating, the brakes remain automatically
applied after the driver releases the brak e pedal. The stop lights and the high
mounted stoplight turn on.
●Hill-start assist control operates for about 2 seconds after the brake pedal is
released.
●If the slip indicator does not flash and the buzzer does not sound when the brake
pedal is further depressed, slightly redu ce the pressure on the brake pedal (do
not allow the vehicle to roll backward) and then firmly depress it again. If the sys -
tem still does not operate, check if th e
operating conditions explained above
have been met.
Hill-start assist control helps to prevent the vehicle from rolling backwards
when starting on an incline or slippery slope.
To engage hill-start assist con -
trol, further depress the brake
pedal when the v
ehicle is
stopped completely.
A buzzer will sound once to
indicate the system is activated.
The slip indicator will also start
flashing.

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2-4. Using other driving systems
2
When driving
■Hill-start assist control buzzer
●When hill-start assist control is activated, the buzzer will sound once.
●In the following situations, hill-start assist control will be canceled and the
buzzer will sound twice.
• No attempt is made to drive the vehi cle within approximately 2 seconds of
releasing the brake pedal.
•Push the P position switch.
• The parking brake is applied.
• The brake pedal is depressed again.
• The brake pedal has been depressed for more than approximately 3 minutes.
■If the slip indicator comes on
It may indicate a malfunction in th e system. Contact your Lexus dealer.
CAUTION
■Hill-start assist control
●Do not overly rely on hill-start assist cont rol. Hill-start assist control may not oper-
ate effectively on extremely steep inclines or roads covered in ice.
●Do not use hill-start assist control to stop or park the vehicle on an incline. Doing
so may cause an accident.

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2-4. Using other driving systems
Pre-Collision System
: If equipped
When the radar sensor detects an unavoidable frontal collision, safety sys-
tems such as the brakes and seat belts are automatically engaged to lessen
impact and injuries to

occupants as well as vehicle damage.
■Pre-collision seat belts (front seat belts only)
If the pre-collision sensor detects that a collision is unavoidable, the pre-
collision system will roll up the seat belt before the collision occurs. 
The same will happen if the driver makes an emergency braking or loses
contr
ol of the vehicle. ( P. 74 )
However, when the TRAC/VSC systems are disabled, the system will not
oper
ate in the event of skidding.
■Pre-collision brake assist
When there is a high possibility of a frontal collision, the system applies
greater braking force in relation to how strongly the brake pedal is
depressed.
■Pre-collision braking
When there is a high possibility of a frontal collision, the system warns the
driver using a warning light, warning display and buzzer. If the system
determines that a collision is unavoidable, the brakes are automatically
applied to reduce the collision speed. Pre-collision braking can be dis -
abled using the pre-collision braking off button.
■ Driver monitor system (if equipped)
When the system determines that ther e is a possibility of a collision, and
the driver is not facing forward, PC S warnings are given in advance to
warn the driver. If the driver contin ues to be not facing forward, and a
probable collision is detected, PCS in forms the driver of danger by per-
forming slight braking to provide a physically warning (pre-collision alert
br
aking). ( P. 2 3 5)