Toyota Prius Prime (2020 year). Owner's manual - part 25

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5-5. Using the driving support systems

■

If the PCS warning light flashes or illuminates and a warning message is
displayed on the multi-information display
The pre-collision system may be temporarily unavailable or there may be a
malfunction in the system.

●

In  the  following  situations,  the  warning  light  will  turn  off,  the  message  will
disappear and the system will become operational when normal operating
conditions return:
• When the radar sensor or camera sensor or the area around either sen-

sor is hot, such as in the sun

• When the radar sensor or camera sensor or the area around either sen-

sor is cold, such as in an extremely cold environment

• When a front sensor is dirty or covered with snow, etc.
• When the part of the windshield in front of the camera sensor is fogged

up or covered with condensation or ice 
(Defogging the windshield: 

P. 504, 514)

• If the camera sensor is obstructed, such as when the hood is open or a

sticker is attached to the windshield near the camera sensor

●

If  the  PCS  warning  light  continues  to  flash  or  remains  illuminated  or  the
warning message does not disappear even though the vehicle has returned
to normal, the system may be malfunctioning. Have the vehicle inspected by
your Toyota dealer immediately.

■

If VSC is disabled

●

If VSC is disabled (

P. 491), the pre-collision brake assist and pre-collision

braking functions are also disabled.

●

The PCS warning light will turn on and “VSC Turned Off Pre-Collision Brake
System Unavailable” will be displayed on the multi-information display.

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LDA (Lane Departure Alert with steering 

control)

When driving on highways and freeways with white (yellow) lines, this
function alerts the driver when the vehicle might depart from its lane
and provides assistance by operating the steering wheel to keep the
vehicle in its lane.
The  LDA  system  recognizes  visi-
ble  white  (yellow)  lines  with  the
camera sensor on the upper por-
tion of the front windshield.

◆

Lane departure alert function

When  the  system  determines
that  the  vehicle  might  depart
from  its  lane,  a  warning  is  dis-
played  on  the  multi-information
display and the warning buzzer
sounds to alert the driver.

When  the  warning  buzzer
sounds,  check  the  surrounding
road  situation  and  carefully
operate  the  steering  wheel  to
move  the  vehicle  back  to  the
center of the lane.

Summary of functions

Functions included in LDA system

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5-5. Using the driving support systems

◆

Steering control function

When  the  system  determines
that  the  vehicle  might  depart
from  its  lane,  the  system  pro-
vides  assistance  as  necessary
by operating the steering wheel
in  small  amounts  for  a  short
period of time to keep the vehi-
cle in its lane.

If  the  system  detects  that  the
steering  wheel  has  not  been
operated  for  a  fixed  amount  of
time or the steering wheel is not
being  firmly  gripped,  a  warning
is  displayed  on  the  multi-infor-
mation  display  and  the  warning
buzzer sounds.

◆

Vehicle sway warning function

When the vehicle is swaying or
appears as if it may depart from
its  lane  multiple  times,  the
warning  buzzer  sounds  and  a
message  is  displayed  on  the
multi-information display to alert
the driver.

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WARNING

■

Before using LDA system
Do not rely solely upon the LDA system. The LDA system does not auto-
matically drive the vehicle or reduce the amount of attention that must be
paid to the area in front of the vehicle. The driver must always assume full
responsibility for driving safely by paying careful attention to the surround-
ing  conditions and operating the steering wheel to  correct the  path  of  the
vehicle. Also, the driver must take adequate breaks when fatigued, such as
from driving for a long period of time.
Failure to perform appropriate driving operations and pay careful attention
may lead to an accident, resulting in death or serious injury.

■

To avoid operating LDA system by mistake
When not using the LDA system, use the LDA switch to turn the system off.

■

Situations unsuitable for LDA system
Do not use the LDA system in the following situations.
The system may not operate properly and lead to an accident, resulting in
death or serious injury.

●

A spare tire, tire chains, etc. are equipped.

●

When the tires have been excessively worn, or when the tire inflation pres-
sure is low.

●

Tires  which  differ  by  structure,  manufacturer,  brand  or  tread  pattern  are
used.

●

Objects  or  patterns  that  could  be  mistaken  for  white  (yellow)  lines  are
present on the side of the road (guardrails, curbs, reflective poles, etc.).

●

Vehicle is driven on a snow-covered road.

●

White (yellow) lines are difficult to see due to rain, snow, fog, dust, etc.

●

Asphalt  repair  marks,  white  (yellow)  line  marks,  etc.  are  present  due  to
road repair.

●

Vehicle is driven in a temporary lane or restricted lane due to construction
work.

●

Vehicle is driven on a road surface which is slippery due to rainy weather,
fallen snow, freezing, etc.

●

Vehicle is driven in traffic lanes other than on highways and freeways.

●

Vehicle is driven in a construction zone.

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5-5. Using the driving support systems

Press  the  LDA  switch  to  turn  the
LDA system on.

The  LDA  indicator  illuminates  and
a  message  is  displayed  on  the
multi-information display.
Press the LDA switch again to turn
the LDA system off.
When the LDA system is turned on
or off, operation of the LDA system
continues  in  the  same  condition
the  next  time  the  hybrid  system  is
started.

WARNING

■

Preventing  LDA  system  malfunctions  and  operations  performed  by
mistake

●

Do not modify the headlights or place stickers, etc. on the surface of the
lights.

●

Do  not  modify  the  suspension  etc.  If  the  suspension  etc.  needs  to  be
replaced, contact your Toyota dealer.

●

Do not install or place anything on the hood or grille. Also, do not install a
grille guard (bull bars, kangaroo bar, etc.).

●

If your windshield needs repairs, contact your Toyota dealer.

Turning LDA system on

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LDA indicator
Illuminates  when  the  LDA  sys-
tem is on.
Steering  control  indicator  and
operation  display  of  steering
wheel operation support
When  that  steering  wheel
assistance  of  the  steering  con-
trol  function  is  operating,  the
indicator  illuminates  and  the
operation  display  on  the  multi-
information display is turned on.
Lane departure alert function display
Displayed  when  the  multi-information  display  is  switched  to  the

 screen. (

P. 243)

Indications on combination meter

1

2

3



Inside  of  displayed  white  lines
is white



Inside of displayed white lines
is black

Indicates that the system is recog-
nizing  white  (yellow)  lines.  When
the  vehicle  departs  from  its  lane,
the  white  line  displayed  on  the
side  the  vehicle  departs  from
flashes orange.

Indicates  that  the  system  is  not
able  to  recognize  white  (yellow)
lines or is temporarily canceled.

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Operation conditions of each function

●

Lane departure alert function
This function operates when all of the following conditions are met.
• LDA is turned on.
• Vehicle speed is approximately 32 mph (50 km/h) or more.
• System recognizes white (yellow) lines.
• Width of traffic lane is approximately 9.8 ft. (3 m) or more.
• Turn signal lever is not operated.
• Vehicle is driven on a straight road or around a gentle curve with a radius

of more than approximately 492 ft. (150 m).

• No system malfunctions are detected. (

P. 401)

●

Steering control function
This function operates when all of the following conditions are met in addi-
tion to the operation conditions for the lane departure alert function.

• Setting for 

 (“LDA Steering Assist Mode”) in the 

 screen of

the multi-information display is set to “On”. (

P. 218)

• Vehicle is not accelerated or decelerated by a certain amount or more.
• Steering  wheel  is  not  operated  with  a  steering  force  level  suitable  for

changing lanes.

• ABS, VSC, TRAC and PCS are not operating.
• TRAC or VSC is not turned off.

●

Vehicle sway warning function
This function operates when all of the following conditions are met.

• Setting for 

 (“Lane Sway Warning Status”) in the 

 screen of

the multi-information display is set to “On”. (

P. 218)

• Vehicle speed is approximately 32 mph (50 km/h) or more.
• Width of traffic lane is approximately 9.8 ft. (3 m) or more.
• No system malfunctions are detected. (

P. 401)

■

Temporary cancellation of functions
When the operation conditions are no longer met, a function may be tempo-
rarily canceled. However, when the operation conditions are met again, oper-
ation of the function is automatically restored. (

P. 398)

■

Steering control function
Depending  on  the  vehicle  speed,  lane  departure  situation,  road  conditions,
etc., the driver may not feel the function is operating or the function may not
operate at all.

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■

Lane departure alert function
The warning buzzer may be difficult to hear due to external noise, audio play-
back, etc.

■

Hands off steering wheel warning

If the driver continues to keep their hands off of the steering wheel, a buzzer
sounds and a warning message and the symbol shown in the illustration are
displayed on the multi-information display. This warning also operates in the
same way when the driver continuously operates the steering wheel only a
small amount. Always keep your hands on the steering wheel when using this
system, regardless of warnings.
Depending on the vehicle and road conditions, the warning may not operate.

■

Vehicle sway warning function

■

White (yellow) lines are only on one side of road
The  LDA  system  will  not  operate  for  the  side  on  which  white  (yellow)  lines
could not be recognized.

When  the  system  determines  that  the
driver  has  removed  their  hands  from  the
steering  wheel  while  the  steering  control
function is operating, a warning message
urging  the  driver  to  hold  the  steering
wheel and the symbol shown in the illus-
tration are displayed on the multi-informa-
tion display.

When  the  system  determines  that  the
vehicle is swaying while the vehicle sway
warning  function  is  operating,  a  buzzer
sounds  and  a  warning  message  urging
the driver to rest and the symbol shown in
the  illustration  are  simultaneously  dis-
played on the multi-information display.
Depending on the vehicle and road condi-
tions, the warning may not operate.

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Conditions in which functions may not operate properly
In the following situations, the camera sensor may not detect white (yellow)
lines and various functions may not operate normally.

●

There  are  shadows  on  the  road  that  run  parallel  with,  or  cover,  the  white
(yellow) lines.

●

The vehicle is driven in an area without white (yellow) lines, such as in front
of a tollgate or checkpoint, or at an intersection, etc.

●

The  white  (yellow)  lines  are  cracked,  “Botts’  dots”,  “Raised  pavement
marker” or stones are present.

●

The white (yellow) lines cannot be seen or are difficult to see due to sand,
etc.

●

The vehicle is driven on a road surface that is wet due to rain, puddles, etc.

●

The  traffic lines are yellow (which may be more difficult to  recognize  than
lines that are white).

●

The white (yellow) lines cross over a curb, etc.

●

The vehicle is driven on a bright surface, such as concrete.

●

The vehicle is driven on a surface that is bright due to reflected light, etc.

●

The  vehicle  is  driven  in  an  area  where  the  brightness  changes  suddenly,
such as at the entrances and exits of tunnels, etc.

●

Light from the headlights of an oncoming vehicle, the sun, etc. enters the
camera.

●

The vehicle is driven where the road diverges, merges, etc.

●

The vehicle is driven on a slope.

●

The vehicle is driven on a road which tilts left or right, or a winding road.

●

The vehicle is driven on an unpaved or rough road.

●

The vehicle is driven around a sharp curve.

●

The traffic lane is excessively narrow or wide.

●

The  vehicle  is  extremely  tilted  due  to  carrying  heavy  luggage  or  having
improper tire pressure.

●

The distance to the preceding vehicle is extremely short.

●

The vehicle is moving up and down a large amount due to road conditions
during driving (poor roads or road seams).

●

The headlight lenses are dirty and emit a faint amount of light at night, or the
beam axis has deviated.

●

The vehicle is struck by a crosswind.

●

The vehicle has just changed lanes or crossed an intersection.

●

Snow tires, etc. are equipped.

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Warning message
If  the  following  warning  message  is  displayed  on  the  multi-information  dis-
play, follow the appropriate troubleshooting procedure.

If a different warning message is displayed, follow the instructions displayed
on the screen.

Warning message

Details/Actions

“Lane Departure Alert

Malfunction

Visit Your Dealer”

The  system  may  not  be  operating
properly.

 Have  the  vehicle  inspected  at  your

Toyota dealer.

“Front Camera

Unavailable

See Owner’s Manual”

Dirt,  rain,  condensation,  ice,  snow,
etc.  are  present  on  the  windshield  in
front of the camera sensor.

 Turn  the  LDA  system  off,  remove

any  dirt,  rain,  condensation,  ice,
snow, etc. from the windshield, and
then turn the LDA system back on.

“Front Camera

Unavailable”

The  operation  conditions  of  the  cam-
era  sensor  (temperature, etc.) are not
met.

 When  the  operation  conditions  of

the  camera  sensor  (temperature,
etc.)  are  met,  the  LDA  system  will
become  available.  Turn  the  LDA
system  off,  wait  for  a  little  while,
and then turn the LDA system back
on.

“Lane Departure Alert 

Unavailable”

The  LDA  system  is  temporarily  can-
celed due to a malfunction in a sensor
other than the camera sensor.

 Turn the LDA system off and follow

the  appropriate  troubleshooting
procedures  for  the  warning  mes-
sage.  Afterward,  drive  the  vehicle
for  a  short  time,  and  then  turn  the
LDA system back on.

“Lane Departure Alert 

System is Unavailable 

Below Approx. 

32 MPH.”

The  LDA  system  cannot  be  used  as
the vehicle speed is less than approxi-
mately 32 mph (50 km/h).

 Drive  the  vehicle  at  approximately

32 mph (50 km/h) or more.

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■

Customization
The following settings can be changed.

For how to change settings, refer to P. 244.

Function

Setting details

Lane departure alert function

Adjust alert sensitivity

Steering control function

Turn steering wheel assistance on and off

Vehicle sway warning function

Turn function on and off

Adjust alert sensitivity

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Dynamic radar cruise controlwith full-speed 

range

In vehicle-to-vehicle distance control mode, the vehicle automatically
accelerates, decelerates and stops to match the speed changes of the
preceding vehicle  even  if  the accelerator  pedal  is  not  depressed.  In
constant speed control mode, the vehicle runs at a fixed speed.
Use  the  dynamic  radar  cruise  control  with  full-speed  range  on  free-
ways and highways.
● Vehicle-to-vehicle distance control mode (P. 407)
● Constant speed control mode (P. 414)

Vehicle-to-vehicle 

distance

switch
Indicators
Display
Set speed
Cruise control switch

Summary of functions

1

2
3
4
5

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WARNING

■

Before using dynamic radar cruise control with full-speed range

●

Driving safely is the sole responsibility of the driver. Do not rely solely on
the system, and drive safely by always paying careful attention to your sur-
roundings.

●

The  dynamic  radar  cruise  control  with  full-speed  range  provides  driving
assistance to reduce the driver’s burden. However, there are limitations to
the assistance provided.
Read the following conditions carefully. Do not overly rely on this system
and always drive carefully.
• When the sensor may not be correctly detecting the vehicle ahead:

P. 417

• Conditions  under  which  the  vehicle-to-vehicle  distance  control  mode

may not function correctly:

P. 418

●

Set the speed appropriately depending on the speed limit, traffic flow, road
conditions, weather conditions, etc. The driver is responsible for checking
the set speed.

●

Even when the system is functioning normally, the condition of the preced-
ing  vehicle  as  detected  by  the  system  may  differ  from  the  condition
observed  by  the  driver.  Therefore,  the  driver  must  always  remain  alert,
assess the danger of each situation and drive safely. Relying solely on this
system or assuming the system ensures safety while driving can lead to
an accident, resulting in death or serious injury.

●

Switch the dynamic radar cruise control with full-speed range off using the
“ON-OFF” button when not in use.

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WARNING

■

Cautions regarding the driving assist systems
Observe the following precautions, as there are limitations to the assistance
provided by the system.
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 with full-speed range 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 mecha-
nism that allows careless 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  with  full-speed  range  determines
whether  the  following  distance  between  the  driver’s  own  vehicle  and  a
designated vehicle traveling ahead is within a set range. It is not capable
of making any other type of judgement. Therefore, it is absolutely neces-
sary 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  with  full-speed  range  does not  include
functions which will prevent or avoid collisions with vehicles ahead of your
vehicle. Therefore, if there is ever any possibility of danger, 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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WARNING

■

Situations unsuitable for dynamic radar cruise control with full-speed
range
Do not use dynamic radar cruise control with full-speed range in any of the
following situations.
Doing so may result in inappropriate speed control and could cause an acci-
dent resulting in death or serious injury.

●

Roads where there are pedestrians, cyclists, etc.

●

In heavy traffic

●

On roads with sharp bends

●

On winding roads

●

On slippery roads, such as those covered with rain, ice or snow

●

On steep downhills, or where there are sudden changes between sharp up
and down gradients 
Vehicle speed may exceed the set speed when driving down a steep hill.

●

At entrances to freeways and highways

●

When weather conditions are bad enough that they may prevent the sen-
sors from detecting correctly (fog, snow, sandstorm, heavy rain, etc.)

●

When there is rain, snow, etc. on the front surface of the radar sensor or
camera sensor

●

In traffic conditions that require frequent repeated acceleration and decel-
eration

●

During emergency towing

●

When an approach warning buzzer is heard often

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g

This mode employs a radar sensor to detect the presence of vehicles
up  to  approximately  328  ft.  (100  m)  ahead,  determines  the  current
vehicle-to-vehicle following distance, and operates to maintain a suit-
able following distance from the vehicle ahead.

Note  that  vehicle-to-vehicle  distance  will  close  in  when  traveling  on  long
downhill slopes.

Driving in vehicle-to-vehicle distance control mode