2021 TOYOTA PRIUS key battery

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6-3. Do-it-yourself maintenance
WARNING
■Battery precautions
Observe the following precautions.
Failure to do so may result in death or serious injury.
● Do not swallow the battery. Doing so may cause chemical burns.
● A coin battery or button battery is used in the electronic key. If a battery is
swallowed, it may cause severe chemical burns in as little as 2 hours and
may result in death or serious injury.
● Keep away new and removed batteries from children.
● If the cover cannot be firmly closed, stop using the electronic key and stow
the key in the place where children cannot reach, and then contact your
Toyota dealer.
● If you accidentally swallow a battery or put a battery into a p art of your
body, get emergency medical attention immediately.
■ To prevent battery explosion or leakage of flammable liquid or gas
● Replace the battery with a new battery of the same type. If a w rong type of
battery is used, it may explode.
● Do not expose batteries to extremely low pressure due to high altitude or
extremely high temperatures.
● Do not burn, break or cut a battery.
NOTICE
■For normal operation after replacing the battery
Observe the following precautions to prevent accidents:
● Always work with dry hands.
Moisture may cause the battery to rust.
● Do not touch or move any other component inside the remote cont rol.
● Do not bend either of the battery terminals.

579
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7When trouble arises
7-1. Essential informationEmergency flashers .......... 580
If your vehicle has to be stopped in an
emergency ...................... 581
If the vehicle is trapped in rising water ..................... 582
7-2. Steps to take in an emergency
If your vehicle needs to be towed ......................... 584
If you think something is wrong .............................. 591
If a warning light turns on or a warning buzzer
sounds ............................ 592
If a warning message is displayed......................... 603
If you have a flat tire (vehicles without
spare tire)........................ 611
If you have a flat tire (vehicles with
spare tire)........................ 631
If the hybrid system will not start ........................... 645
If the electronic key does not operate properly ........ 647
If the 12-volt battery is discharged ...................... 650
If your vehicle overheats ... 656
If the vehicle becomes stuck ............................... 661

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7-2. Steps to take in an emergency
If your vehicle needs to be towed
In the following situations, it is not possible to be towed by another
vehicle using cables or chains, as the front wheels may be lock ed due
to the parking lock. Contact your Toyota dealer or commercial towing
service.
● There is a malfunction in t he shift control system. (P. 249, 609)
● There is a malfunction in the immobilizer system. ( P. 95)
● There is a malfunction in the smart key system. (P. 647)
● The 12-volt battery is discharged. ( P. 6 5 0 )
The following may indicate a problem with your hybrid transmiss ion.
Contact your Toyota dealer or commercial towing service before tow-
ing.
● The hybrid system warning message is displayed and the vehicle
does not move.
● The vehicle makes an abnormal sound.
If towing is necessary, we recommend having your vehicle
towed by your Toyota dealer o r commercial towing service,
using a wheel-lift type t ruck or flatbed truck.
Use a safety chain system for all towing, and abide by all stat e/
provincial and local laws.
Situations when it is not possibl e to be towed by another vehicle
Situations when it is necessary to contact dealers before towing

6067-2. Steps to take in an emergency
PRIUS_OM_OM47E09U_(U)■
If “See Owner’s Manual” is shown
●If “Braking Power Low Stop in a Safe Place See Owner’s Manual” is shown,
this may be a malfunction. Immediately stop the vehicle in a sa fe place and
contact your Toyota dealer. Continuing to drive the vehicle may be danger-
ous.
● If “Engine Oil Pressure Low” is shown, this may be a malfunction. Immedi-
ately stop the vehicle in a safe place and contact your Toyota dealer.
● If the following messages are shown, there may be a malfunction . Immedi-
ately have the vehicle inspected by your Toyota dealer.
• “Hybrid System Malfunction”
• “Check Engine”
• “Hybrid Battery System Malfunction”
• “Accelerator System Malfunction”
• “Smart Key System Malfunction See Owner’s Manual”
■ If “Shift System Not A ctive Apply Parking Brake Securely While Parking
See Owner’s Manual” is shown
Indicates a temporary operation failure or malfunction in the shift control sys-
tem. Immediately have the vehicle inspected by your Toyota deal er.
When the message is shown, the hybrid system may not be started or the
shift position may not be changed normally. (Coping method: P. 609)
■ If “Shift System Malfunction A pply Parking Brake Securely While Park-
ing See Owner’s Manual” is shown
Indicates a malfunction in the shift control system. Immediatel y have the vehi-
cle inspected by your Toyota dealer.
When the message is shown, the hybrid system may not be started or the
shift position may not be changed normally. (Coping method: P. 609)
■ If “ Switch Malfunction Apply Par king Brake Securely While Parking
See Owner’s Manual” is shown
The P position switch may not operate. Immediately have the veh icle
inspected by your Toyota dealer.
When parking the vehicle, stop the vehicle on level ground and apply the
parking brake firmly.
■ If “Shift System Malfunction Shi fting Unavailable See Owner’s M anual”
is shown
Indicates a malfunction in the shift control system. Immediatel y have the vehi-
cle inspected by your Toyota dealer.
The shift position may not be shifted from P to other than P.
■ If “Shift System Malfunction S top in a Safe Place See Owner’s Manual”
is shown
Indicates a malfunction in the shift control system. Immediatel y have the vehi-
cle inspected by your Toyota dealer.
The shift position may not be changed. Stop the vehicle in a sa fe place.

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7
When trouble arises
7-2. Steps to take in an emergency
If the hybrid system will not start
One of the following may be the cause of the problem:
● The electronic key may no t be functioning properly.
* ( P. 647)
● There may not be sufficient f uel in the vehicle’s tank.
Refuel the vehicle. ( P. 90)
● There may be a malfunction in the immobilizer system.
* ( P. 9 5 )
● There may be a malfunction i n the shift control system.
*
(  P. 249, 609)
● The hybrid system may be malfunc tioning due to an electrical prob-
lem such as electronic key battery depletion or a blown fuse. H ow-
ever, depending on the type of malfunction, an interim measure is
available to start the hybrid system. ( P. 646)
● There is a possibility that the t emperature of the hybrid battery
(traction battery) is extremely low (approximately below -22°F
[-30°C]). ( P. 90, 248)
*: It may not be possible to shift the shift position other than P.
One of the following may be the cause of the problem:
● The 12-volt battery may be discharged. ( P. 650)
● The 12-volt battery terminal connections may be loose or corrod ed.
(  P. 524)
Reasons for the hybrid system not starting vary depending on
the situation. Check the followi ng and perform the appropriate
procedure:
The hybrid system will not start even though the correct starting
procedure is being followed. ( P. 245)
The interior lights and headlights are dim, or the horn does no t
sound or sounds at a low volume.

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7
When trouble arises
7-2. Steps to take in an emergency
If the electronic key does not operate
properly
Use the mechanical key (P. 181) in order to perform the following
operations:
Locks all the doors
Closes the windows and moon
roof
*1 (turn and hold)*2
Unlocks the door
Turning the key rearward unlocks
the driver’s door. Turning the key
once again within 3 seconds
unlocks the other doors.
Opens the windows and moon roof*1 (turn and hold)*2
*1: If equipped
*2: This setting must be customized at your Toyota dealer. ( P. 690)
If communication between the electronic key and vehicle is
interrupted ( P. 198) or the electronic key cannot be used
because the battery is depleted, the smart key system and
wireless remote control can not be used. In such cases, the
doors can be opened and the hybrid system can be started by
following the procedure below.
Locking and unlocking the doors
1
2
3
4

6497-2. Steps to take in an emergency
PRIUS_OM_OM47E09U_(U)
7
When trouble arises
■Stopping the hybrid system
Set the parking brake, shift the shift position to P and press the power switch
as you normally do when stopping the hybrid system.
■ Replacing the key battery
As the above procedure is a temporary measure, it is recommende d that the
electronic key battery be replaced immediately when the battery is depleted.
( P. 560)
■ Changing power switch modes
Release the brake pedal and press the power switch in step abo ve. The
hybrid system does not start and modes will be changed each tim e the switch
is pressed. ( P. 247)
■ When the electronic key does not work properly
●Make sure that the smart key system has not been deactivated in the cus-
tomization setting. If it is off, turn the function on.
(Customizable features: P. 690)
● Check if battery-saving mode is set. If it is set, cancel the f unction.
( P. 198)
WARNING
■ When using the mechanical key and operating the power windows o r
moon roof (if equipped)
Operate the power window or moon roof after checking to make su re that
there is no possibility of any passenger having any of their body parts
caught in the window or moon roof.
Also, do not allow children to operate the mechanical key. It is possible for
children and other passengers to get caught in the power window or moon
roof.
3

6537-2. Steps to take in an emergency
PRIUS_OM_OM47E09U_(U)
7
When trouble arises
■When recharging or replacing the 12-volt battery
●In some cases, it may not be possible to unlock the doors using the smart
key system when the 12-volt battery is discharged. Use the wire less remote
control or the mechanical key to lock or unlock the doors.
● The hybrid system may not start on the first attempt after the 12-volt battery
has recharged but will start normally after the second attempt. This is not a
malfunction.
● The power switch mode is memorized by the vehicle. When the 12- volt bat-
tery is reconnected, the system will return to the mode it was in before the
12-volt battery was discharged. Before disconnecting the 12-volt battery,
turn the power switch off.
If you are unsure what mode the power switch was in before the 12-volt bat-
tery discharged, be especially careful when reconnecting the 12 -volt battery.
● If the 12-volt battery discharges while the shift position is in P, it may not be
possible to shift the shift position to other positions. In thi s case, the vehicle
cannot be towed without lifting both front wheels because the f ront wheels
will be locked. ( P. 584)
■ When replacing the 12-volt battery
●Use a 12-volt battery that conforms to European regulations.
● Use a 12-volt battery that the case size is same as the previou s one (LN1),
20 hour rate capacity (20HR) is equivalent (45Ah) or greater, and perfor-
mance rating (CCA) is equivalent (295A) or greater.
• If the sizes differ, the 12-volt battery cannot be properly se cured.
• If the 20 hour rate capacity is low, even if the time period w here the vehi-
cle is not used is a short time, the 12-volt battery may discharge and the
hybrid system may not be able to start.
● For details, consult your Toyota dealer.