brake TOYOTA PRIUS PHV 2012 Service Manual

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2-4. Using other
driving systems
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2
When driving
Approach warning
When your vehicle is too close to a vehicle ahead, and sufficient
automatic deceleration via the cruise control is not possible, the dis-
play will flash and the buzzer will sound to alert the driver. An exam-
ple of this would be if another driver cuts in front of you while you are
following a vehicle. Apply the brakes to ensure an appropriate vehi-
cle-to-vehicle distance.
■ Warnings may not occur when
In the following instances, there is a possibility that the warnings
will not occur:
● When the speed of the vehicl e ahead matches or exceeds your
vehicle speed
● When the vehicle ahead is traveling at an extremely slow speed
● Immediately after the cruise control speed was set
● At the instant the accelerator is applied

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CAUTION
■Before using dynamic radar cruise control
Do not overly rely on vehicle-to-vehicle distance control.
Be aware of the set speed. If automatic deceleration/acceleration is not
appropriate, adjust the vehicle speed, as well as the distance between your
vehicle and vehicles ahead by applying the brakes etc.
■ Cautions regarding the driving assist systems
Observe the following precautions.
Failure to do so may cause an accident resulting in death or serious injury.
● Assisting the driver to measure following distance
The dynamic radar cruise control is only intended to help the driver in
determining the following distance between the driver’s own vehicle and a
designated vehicle traveling ahead. It is not a mechanism that allows care-
less or inattentive driving, and it is not a system that can assist the driver in
low-visibility conditions. It is still necessary for driver to pay close attention
to the vehicle’s surroundings.
● Assisting the driver to judge proper following distance
The dynamic radar cruise control determines whether the following dis-
tance between the driver’s own vehicle and a designated vehicle traveling
ahead is appropriate or not. It is not capable of making any other type of
judgement. Therefore, it is absolutely necessary for the driver to remain
vigilant and to determine whether or not there is a possibility of danger in
any given situation.
● Assisting the driver to operate the vehicle
The dynamic radar cruise control has no capability to prevent or avoid a
collision with a vehicle traveling ahead. Therefore, if there is ever any dan-
ger, the driver must take immediate and direct control of the vehicle and
act appropriately in order to ensure the safety of all involved.

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CAUTION
■When the sensor may not be correctly detecting the vehicle ahead
Apply the brakes as necessary when any of the following types of vehicles
are in front of you.
As the sensor may not be able to correctly detect these types of vehicles,
the approach warning ( P. 319) will not be activated, and a fatal or serious
accident may result.
● Vehicles that cut in suddenly
● Vehicles traveling at low speeds
● Vehicles that are not moving
● Vehicles with small rear ends (trailers with no load on board etc.)
● Motorcycles traveling in the same lane
■ 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 sen-
sor may not be able to correctly detect vehicles ahead, and a fatal or serious
accident may result:
● When water or snow thrown up by the surrounding vehicles hinders the
functioning of the sensor
● When your vehicle is pointing upwards (caused by a heavy load in the lug-
gage compartment 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

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Driving assist systems
To help enhance driving safety and performance, the following sys-
tems operate automatically in res ponse to various driving situations.
Be aware, however, that these systems are supplementary and
should not be relied upon too h eavily 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)
Helps to maintain drive power and prevent 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
surfaces by controlling steering performance.

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■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 forcefully or repeatedly, or 1-2 minutes after the hybrid sys-
tem 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
operating. 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 slightly after the ABS is activated.
■ EPS operation sound
When the steering wheel is operated, a motor sound (whirring sound) may
be heard. This does not indicate a malfunction.
■ Reduced effectiveness of the EPS system
The effectiveness of the EPS system 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 hybrid
system off. The EPS system should return to normal within 10 minutes.
■ Electric power steering system warning light
 P. 540

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2-4. Using other driving systems
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2
When driving
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 automati-
cally applied after the driver releases the brake 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 reduce the pressure on the
brake pedal (do not allow the vehicl e to roll backward) and then firmly
depress it again. If the system still does not operate, check if the operat-
ing 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 vehicle is
stopped completely.
A buzzer will sound once to
indicate the system is acti-
vated. The slip indicator will
also start flashing.

334 2-4. Using other driving systems
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■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 vehicle 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 light comes on
It may indicate a malfunction in the system. Contact your Toyota dealer.
CAUTION
■Hill-start assist control
● Do not overly rely on the hill-start assist control. Hill-start assist control
may not operate effectively on extremely steep inclines or roads covered
in ice.
● Unlike the parking brake, hill-start assist control is not intended to hold the
vehicle stationary for an extended period of time. Do not attempt to use
hill-start assist control to hold the vehicle on an incline for an extended
period of time, as doing so may lead to an accident.

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2
When driving
PCS (Pre-Collision System)
: If equipped
When the radar sensor detects possibility of a frontal collision, the
pre-collision systems such as the brakes and seat belts are automat-
ically engaged to lessen impact 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 retract the seat belt before the collision occurs.
The same will happen if the driver makes an emergency braking or
loses control of the vehicle. ( P. 158)
However, when the VSC system is 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 sys-
tem determines that a collision is unavoidable, the brakes are automat-
ically applied to reduce the collision speed. Pre-collision braking can be
disabled using the pre-collision braking off switch.

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2-4. Using other
driving systems
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When driving
■The pre-collision system is operational when
● Pre-collision seat belts (type A)
• Vehicle speed is greater than about 19 mph (30 km/h).
• The system detects sudden braking or skidding.
• The front occupants are wearing a seat belt.
● Pre-collision seat belts (type B)
• Vehicle speed is greater than about 4 mph (5 km/h).
• The speed at which your vehicle is approaching the obstacle or the
vehicle running ahead of you is greater than about 19 mph (30 km/h).
• The front occupants are wearing a seat belt.
● Pre-collision brake assist:
• Vehicle speed is greater than about 19 mph (30 km/h).
• The speed at which your vehicle is approaching the obstacle or the
vehicle running ahead of you is greater than about 19 mph (30 km/h).
• The brake pedal is depressed.
● Pre-collision braking:
• Vehicle speed is greater than about 10 mph (15 km/h).
• The speed at which your vehicle is approaching the obstacle or the
vehicle running ahead of you is greater than about 10 mph (15 km/h).
• The pre-collision braking off switch is not pressed.

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■Conditions that may trigger the system even if there is no possibility of
a collision
● When there is an object by the roadside at the entrance to a curve
● When passing an oncoming vehicle on a curve
● When driving over a narrow iron bridge
● When there is a metal object on the road surface
● When driving on an uneven road surface (nose up, nose down)
● When passing an oncoming vehicle on a left-turn
● When your vehicle rapidly closes on the vehicle in front
● When a grade separation/interchange, sign, billboard, or other structure
appears to be directly in the vehicle’s line of travel
● When the steep angle of the road causes a metal object located beneath
the road surface to be seen ahead of the vehicle
● When an extreme change in vehicle height occurs
● When the axis of the radar is out of adjustment
● When passing through certain toll gates
● When passing through an overpass
When the system is activated in the situations described above, there is also
a possibility that the seat belts will retract quickly and the brakes will be
applied with a force greater than normal. When the seat belt is locked in the
retracted position, stop the vehicle in a safe place, release the seat belt and
refasten it.