Wheel Lexus IS250 2010 Service Manual

150
2-1. Driving procedures
IS350/250_U
Horn
■After adjusting the steering wheel (vehicles with manually adjustable type steer-
ing wheel)
Make sure that the steering wheel is securely locked.
The horn may not sound if the steering wheel is not securely locked. (→P. 6 9 )
To sound the horn, press on or
close to the mark.

189
2-4. Using other driving systems
2
When driving
IS350/250_U
CAUTION
■Conditions under which the vehicle-to-vehicle distance control may not function
correctly
Apply the brakes as necessary in the following conditions as the radar sensor may
not be able to correctly detect vehicles ahead, and an accident may result.
●When water or snow thrown up by the surrounding vehicles hinders the function-
ing of the sensor
●When your vehicle is pointing upwards (caused by a heavy load in the trunk, etc.)
●When the road curves or when the lanes are narrow
●When steering wheel operation or your position in the lane is unstable
●When the vehicle ahead of you decelerates suddenly
■Handling the radar sensor
Observe the following to ensure the cruise control system can function effectively:
●Keep the sensor and front grille clean at all times.
Clean the sensor and front grille with a soft cloth so you do not mark or damage
them.
●Do not subject the sensor or surrounding area to a strong impact.
If the sensor moves even slightly off position, the system may malfunction. If the
sensor or surrounding area is subject to a strong impact, always have the area
inspected and adjusted by a Lexus dealer.
●Do not disassemble the sensor.
●Do not attach accessories or stickers to the sensor, grille or surrounding area.
●Do not modify or paint the sensor and grille.
■To ensure the radar sensor functions correctly
Do not do the following to the sensor or grille cover as doing so may cause the sen-
sor not to function correctly and could result in an accident.
●Stick or attach anything to them
●Leave them dirty
●Disassemble, or subject them to strong shocks
●Modify or paint them
●Replace them with non-genuine parts

196
2-4. Using other driving systems
IS350/250_U
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 when swerving suddenly or turning on
slippery road surfaces.
■TRAC (Traction Control)
Maintains drive power and prevents the rear wheels (2WD models) or all
wheels (AWD models) from spinning wh en starting the vehicle or acceler-
ating on slippery roads.
■ Hill-start assist control (vehicles with an automatic transmission)
Prevents the vehicle from rolling backwards when starting on an incline or
slippery slope.
■EPS (Electric Power Steering)
Employs an electric motor to reduce the amount of effort needed to turn
the steering wheel.

197
2-4. Using other driving systems
2
When driving
IS350/250_U
When the VSC/TRAC/hill-start assist control systems are operatingIf the vehicle is in danger of slip-
ping, rolling backwards when
starting on an incline, or if the rear
wheels (2WD) or 4 wheels
(AWD) spin, the slip indicator light
flashes to indicate that the VSC/
TRAC/hill-start assist control sys-
tems have been engaged.
A buzzer (intermittent) sounds to
indicate that VSC is operating.
The stop lights and high mounted
stoplight turn on when the hill-start
assist control system is operating.
■VDIM (Vehicle Dynamics Integrated Management)
Provides integrated control of the ABS, brake assist, TRAC, VSC, hill-start
assist control, and EPS systems.
Maintains vehicle stability when swerving on slippery road surfaces by
controlling the brakes and engine output.
■PCS (Pre-Collision System) (if equipped)
→ P. 2 0 2

198
2-4. Using other driving systems
IS350/250_U
To disable TRAC/VSCIf the vehicle gets stuck in fresh snow or mud, TRAC and VSC may
reduce power from the engine to the wheels. You may need to turn the
system off to enable you to rock the vehicle in order to free it.
■ Turning off TRAC
Quickly push and release the but-
ton to turn off TRAC.
A message will be shown on the
multi-information display.
Push the button again to turn the
system back on.
■Turning off TRAC and VSC
Push and hold the button for more
than 3 seconds while the vehicle is
stopped to turn off TRAC and
VSC.
A message will be shown on the
multi-information display and the
VSC off indicator light will come
on.
Push the button again to turn the
system back on.

200
2-4. Using other driving systems
IS350/250_U
■Hill-start assist control is operational when
●The shift lever is in the D or S position.
●The brake pedal is not depressed.
■EPS operation sound
When the steering wheel operates, a motor sound (whirring sound) may be heard.
This does not indicate a malfunction.
■Reduced effectiveness of EPS
The effectiveness of EPS is reduced to prevent the system from overheating 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 engine OFF. The system should return to normal within
10 minutes.
■If the slip indicator comes on
It may indicate a malfunction in the VSC, TRAC or hill start assist control function.
Contact your Lexus dealer.
CAUTION
■The ABS does not operate effectively when
●The limits of tire gripping performance have been exceeded.
●The vehicle hydroplanes while driving at high speed on the 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 distance. 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

201
2-4. Using other driving systems
2
When driving
IS350/250_U
CAUTION
■TRAC may not operate effectively when
Directional control and power may not be achievable 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.
■If hill-start assist control does not operate effectively
(vehicles with an automatic transmission)
Do not overly rely on the hill-start assist control. The hill-start assist control may not
operate effectively on steep inclines and roads covered in ice.
■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 TRAC and VSC are off
Be especially careful and drive at a speed appropriate to the road conditions. As
these are systems to ensure vehicle stability and driving force, do not turn off TRAC
and VSC unless necessary.
■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
pressure level.
The ABS and VSC systems will not function correctly if different tires are fitted on
the vehicle.
Contact your Lexus dealer for further information when replacing tires or wheels.
■Handling of tires and suspension
Using tires with any kind of problem or modifying the suspension will affect the driv-
ing assist systems, and may cause the system to malfunction.

210
2-5. Driving information
IS350/250_U
Winter driving tips
Carry out the necessary preparations and inspections before driving the
vehicle in winter. Always drive the vehicle in a manner appropriate to the
prevailing weather conditions.
■Pre-winter preparations
● Use fluids that are appropriate to the prevailing outside tempera-
tures.
• Engine oil
• Engine coolant
• Washer fluid
● Have a service technician inspect the level and specific gravity of
battery electrolyte.
● Have the vehicle fitted with four snow tires or purchase a set of
tire chains for the rear tires.
Ensure that all tires are the specified size and the same brand, and that
chains match the size of the tires.
■Before driving the vehicle
Perform the following according to the driving conditions.
● Do not try to forcibly open a window or move a wiper that is fro-
zen. Pour warm water over the frozen area to melt the ice. Wipe
away the water immediately to prevent it from freezing.
● To ensure proper operation of the climate control system fan,
remove any snow that has accumulated on the air inlet vents in
front of the windshield.
● Remove any ice that has accumulated on the vehicle chassis.
● Periodically check for and remove any excess ice or snow that
may have accumulated in the wheel well or on the brakes.

211
2-5. Driving information
2
When driving
IS350/250_U
Selecting tire chainsTire chains can be mounted on 16- and 17-inch tires. They cannot be
mounted on 18-inch tires. Use the correct tire chain size when mounting
the tire chains. Chain size is regulated for each tire size. Side chain
(0.12 in. [3 mm] in diameter)
Cross chain
(0.16 in. [4 mm] in diameter)
Regulations on the use of tire chains
● Regulations regarding the use of tire chains vary according to location
and type of road. Always check local regulations before installing
chains.
● Install the chains on the rear tires.
● Retighten the chains after driving 1 /4  1 /2 mile (0.5  1.0 km).
■When driving the vehicle
Accelerate the vehicle slowly and drive at a reduced speed suitable
to road conditions.
■ When parking the vehicle
Park the vehicle and move the shift lever to P (automatic transmis-
sion) or 1 or R (manual transmission) without setting the parking
brake. The parking brake may freeze up, preventing it from being
released. If necessary, block the wheels to prevent inadvertent slid-
ing or creeping.

212
2-5. Driving information
IS350/250_U
■Snow chain installation
Observe the following precautions when installing and removing chains.
●Install and remove tire chains in a safe location.
●Install tire chains on the rear tires only. Do not install tire chains on front tires.
●Install the tire chains on rear tires as tightly as possible. Retighten chains after
driving 1 /4 - 1 /2 mile (0.5 - 1.0 km).
●Install tire chains following the instructions provided in the accompanying
instructions.
CAUTION
■Driving with snow tires
Observe the following precautions to reduce the risk of accidents.
Failing to do so may result in a loss of vehicle control and cause death or serious
injury.
●Use tires of the size specified for your vehicle.
●Maintain the recommended level of air pressure.
●Do not drive in excess of 75 mph (120 km/h), regardless of the type of snow tires
being used.
●Use snow tires on all, not just some wheels.
■Driving with tire chains
Observe the following precautions to reduce the risk of accidents.
Failing to do so may result in the vehicle being unable to be driven safely, and may
cause death or serious injury.
●Do not drive in excess of the speed limit specified for the tire chains being used,
or 30 mph (50 km/h), whichever is lower.
●Avoid driving on bumpy road surfaces or over potholes.
●Avoid sudden turns and braking, as use of chains may adversely affect vehicle
handling.
●Slow down sufficiently before entering a curve to ensure that vehicle control is
maintained.