2022 TOYOTA MIRAI Owners Manual

4738-2. Steps to take in an emergency
Owners Manual_USA_M62084_en
8
When trouble arises
■Starting the fuel cell system
when the 12-volt battery is dis-
charged
The fuel cell system cannot be
started by push-starting.
■To prevent 12-volt battery dis-
charge
●Turn off the headlights and the
audio system while the fuel cell
system is off.
●Turn off any unnecessary electri-
cal components when the vehicle
is running at a low speed for an
extended period, such as in heavy
traffic.
■When the 12-volt battery is
removed or discharged
●Information stor ed in the ECU is
cleared. When the 12-volt battery
is depleted, have the vehicle
inspected at you r Toyota dealer.
●Some systems may require initial-
ization. ( P.510)
●If the 12-volt battery discharges, it
may not be possible to shift the
shift position to other positions.
In this case, the vehicle cannot be
towed without lifting both rear
wheels because the rear wheels will
be locked.
■When removing the 12-volt bat-
tery terminals
When the 12-volt battery terminals
are removed, the information stored
in the ECU is cleared. Before
removing the 12-volt battery termi-
nals, contact your Toyota dealer.
■Charging the 1 2-volt battery
The electricity stor ed in the 12-volt
battery will discharge gradually even
when the vehicle is not in use, due
to natural discharge and the drain-
ing effects of certain electrical appli-
ances. If the vehicle is left for a long
time, the 12-volt battery may dis-
charge, and the fuel cell system
may be unable to s tart. (The 12-volt battery recharges automatically
while the fuel cell
system is operat-
ing.)
■When recharging or replacing
the 12-volt battery
●In some cases, it may not be pos-
sible to unlock the doors using the
smart key system when the 12-
volt battery is discharged. Use the
wireless remote c ontrol or the
mechanical key to lock or unlock
the doors.
●The fuel cell 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 memo-
rized by the vehicle. When the 12-
volt battery is reconnected, the
system will return to the mode it
was in before the 12-volt battery
was discharged. Before discon-
necting the 12-volt battery, turn
the power switch off.
If you are unsure what mode the
power switch was in before the
12-volt battery discharged, be
especially careful when recon-
necting the 12-volt battery.
●When the 12-volt battery is recon-
nected, start the fuel cell system,
depress the brake pedal, and con-
firm that it is possible to shift into
each shift position.
●If the battery is removed or the ter-
minals disconnected without oper-
ating the water release function
during cold weather, the vehicle
may not start due to the fuel cell
system being frozen. To prevent
this, operate th e water release
function before removing the bat-
tery or disconnecting the termi-
nals. ( P.189)
■When replacing t he 12-volt bat-
tery
●Use a Central De gassing type 12-
volt battery (European Regula-
tions).

4748-2. Steps to take in an emergency
Owners Manual_USA_M62084_en
●Use a 12-volt battery with the
same case size as the previous
12-volt battery and an equivalent
20 hour rate capacity (20HR) or
greater.
• If the sizes differ, the 12-volt bat-
tery cannot be properly secured.
• If the 20 hour rate capacity is low,
even if the time period where the
vehicle is not used is a short time,
the 12-volt battery may discharge
and the fuel cell system may not
be able to start.
●Use a 12-volt battery with a han-
dle. If a 12-volt b attery without a
handle is used, removal is more
difficult.
●After replacing, firmly attach the
following items to the exhaust hole
of the 12-volt battery.
• Use the exhaust hose that was attached to the 12-volt battery
before replacing an d confirm that
it is firmly connected to the hole
section of t he vehicle.
• Use the exhaust hole plug included with the 12-volt battery
replaced or the one installed on
the 12-volt battery prior to the
replacement. (Depending on the
12-volt battery to be replaced, the
exhaust hole may be plugged.)
Exhaust hole plug
Exhaust hole
Exhaust hose
For details, consult your Toyota
dealer.
WARNING
■When removing the 12-volt
battery terminals
Always remove the negative (-)
terminal first. If the positive (+) ter-
minal contacts any metal in the
surrounding area when the posi-
tive (+) terminal is removed, a
spark may occur, leading to a fire
in addition to ele ctrical shocks
and death or serious injury.
■Avoiding 12-volt battery fires
or explosions
Observe the following precautions
to prevent accidentally igniting the
flammable gas that may be emit-
ted from the 12-volt battery:
●Make sure each jumper cable is
connected to the correct termi-
nal and that it is not unintention-
ally in contact with any other
than the intended terminal.
●Do not allow the other end of
the jumper cable connected to
the “+” terminal to come into
contact with any other parts or
metal surfaces in the area, such
as brackets or unpainted metal.
●Do not allow the + and - clamps
of the jumper cables to come
into contact with each other.
●Do not smoke, use matches,
cigarette lighter s or allow open
flame near the 1 2-volt battery.
■12-volt battery precautions
The 12-volt battery contains poi-
sonous and corrosive acidic elec-
trolyte, while related parts contain
lead and lead compounds.
Observe the following precautions
when handling the 12-volt battery:

4758-2. Steps to take in an emergency
Owners Manual_USA_M62084_en
8
When trouble arises
WARNING
●When working with the 12-volt
battery, always wear safety
glasses and take care not to
allow any battery fluids (acid) to
come into contact with skin,
clothing or the vehicle body.
●Do not lean over the 12-volt bat-
tery.
●In the event that battery fluid
comes into contact with the skin
or eyes, immediately wash the
affected area with water and
seek medical attention. Place a
wet sponge or cloth over the
affected area until medical
attention can be received.
●Always wash your hands after
handling the 12-volt battery sup-
port, terminals, and other bat-
tery-related parts.
●Do not allow child ren near the
12-volt battery.
■After recharging the 12-volt
battery
Have the 12-volt battery
inspected at your Toyota dealer
as soon as possible.
If the 12-volt battery is deteriorat-
ing, continued use may cause the
12-volt battery to emit a malodor-
ous gas, which may be detrimen-
tal to the health of passengers.
■When replacing the 12-volt
battery
●When the vent plug and indica-
tor are close to the hold down
clamp, the battery fluid (sulfuric
acid) may leak.
●For information regarding 12-
volt battery rep lacement, con-
tact your Toyota dealer.
●After replacing, s ecurely attach
the exhaust hose and exhaust
hole plug to the exhaust hole of
the replaced 12-volt battery. If
not properly installed, gases
(hydrogen) may leak into the
vehicle interior, and there is the
possible danger of the gas ignit-
ing and exploding.
NOTICE
■When handling jumper cables
When connecting the jumper
cables, ensure that they do not
become entangled in the cooling
fan.
■To prevent damaging the
vehicle
The exclusive jump starting termi-
nal is to be used when charging
the 12-volt battery from another
vehicle in an emergency. It cannot
be used to jump start another
vehicle.

4768-2. Steps to take in an emergency
Owners Manual_USA_M62084_en
Label
Fuel cell stack coolant reservoir
Inverter coolant reservoir
If your vehicle overheats
The following may indicate that your vehicle is overheating.
The high coolant temperature warning light ( P.442) comes on
or flashes, or a loss of fuel cell system power is experienced.
(For example, the vehicle speed does not increase.)
 The fuel cell system overheat warning light ( P.442) comes on
 Steam comes out from under the hood.
Parts name for cooling components

4778-2. Steps to take in an emergency
Owners Manual_USA_M62084_en
8
When trouble arises
If the high coolant tempera-
ture warning light comes on or
flashes
1 Stop the vehicle in a safe
place and turn off the air con-
ditioning system, and then
stop the fuel cell system.
2 If you see steam:
Carefully lift the hood after
the steam subsides.
If you do not see steam:
Carefully lift the hood.
3 After the fuel cell system has
cooled down sufficiently,
inspect the hoses and radia- tor core (radiator) for any
leaks.
Electric cooling fan
Fuel cell stack coolant radia-
tor
If a large amount of coolant leaks,
immediately contact your Toyota
dealer.
4
The fuel cell stack coolant
level is satisfactory if it is
between the “MAX” and
“MIN” lines on the reservoir.
Fuel cell stack coolant reser-
voir
“MAX” line
“MIN” line
If the amount of fuel cell stack
coolant is low:
Immediately contact your Toyota
dealer.
NOTICE
■Fuel cell stack coolant
The fuel cell stack coolant is
exclusive for fuel cell stack usage.
Damage may occur when water
or any other type of coolant is
used, so never use any other
fluid. If the fuel cell stack coolant
is low, immediately contact your
Toyota dealer.
Correction procedures

4788-2. Steps to take in an emergency
Owners Manual_USA_M62084_en
If the amount of fuel cell stack
coolant is not low:
Have the vehicle inspected at
the nearest Toyota dealer.
Even if the fuel cell stack cool-
ant is low, do not refill it.
If the fuel cell system over-
heat warning light comes on
1 Stop the vehicle in a safe
place and turn off the air con-
ditioning system, and then
stop the fuel cell system.
2 If you see steam or coolant
leaks:
Carefully lift the hood after
the steam subsides.
If you do not see steam or
coolant leaks:
Carefully lift the hood.
3 After the fuel cell system has
cooled down, inspect the hoses and radiator core (radi-
ator) for any leaks.
Electric cooling fan
Inverter coolant radiator
If a large amount of coolant leaks,
immediately contact your Toyota
dealer.
4
The inverter coolant level is
satisfactory if it is between
the “MAX” and “MIN” lines on
the reservoir.
Inverter coolant reservoir
“MAX” line
“MIN” line
5 Add inverter coolant if neces-
sary.
Water can be used in an emer-
gency if inverter coolant is unavail-

4798-2. Steps to take in an emergency
Owners Manual_USA_M62084_en
8
When trouble arises
able.
6 Start the fuel cell system and
turn the air conditioning sys-
tem on to check that the radi-
ator cooling fan operate and
to check for coolant leaks
from the radiator or hoses.
The fan operate when the air condi-
tioning system is turned on immedi-
ately after a cold s tart. Confirm that
the fan is operating by checking the
fan sound and air flow. If it is diffi-
cult to check these, turn the air con-
ditioning system on and off
repeatedly.
(The fan may not o perate in freez-
ing temperatures.)
7 If the fan is not operating:
Stop the fuel cell system
immediately and contact your
Toyota dealer.
If the fan is operating:
Have the vehicle inspected at
the nearest Toyota dealer.
WARNING
■When inspecting under the
hood of your vehicle
Observe the following precau-
tions.
Failure to do so may result in seri-
ous injury such as burns.
●If steam is seen coming from
under the hood, do not open the
hood until the steam has sub-
sided. The fuel cell unit com-
partment may be very hot.
●Even if fuel cell system has
stopped, the cooling fan may
begin to move suddenly.
Do not touch or approach the
rotating parts of the fan. Doing
so may lead to fingers, clothes
or tools getting caught, resulting
in injury.
●Do not loosen the coolant reser-
voir caps or radia tor cap, while
the fuel cell system and radiator
are hot.
High temperature steam or
coolant could spray out.
NOTICE
■When inverter coolant
Add coolant slowly after the fuel
cell system has cooled down suffi-
ciently. Adding inverter cool cool-
ant to a hot fuel cell system too
quickly can cause damage to the
fuel cell system.
■To prevent damage to the
cooling system
Observe the following precau-
tions:
●Avoid contaminating the coolant
with foreign matter (such as
sand or dust etc.).
●Do not use any coolant additive
with inverter coolant.
●For replacement of the fuel cell
stack coolant, contact your Toy-
ota dealer.
●Do not use water or any other
coolant when refilling the fuel
cell stack coolant. Also, do not
use any additive agents for the
coolant.

4808-2. Steps to take in an emergency
Owners Manual_USA_M62084_en
1Set the parking brake and
stop the fuel cell system.
2 Remove the mud, snow or
sand from around the rear
wheels.
3 Place wood, stones or some
other material under the rear
wheels to help provide trac-
tion.
4 Restart the fuel cell system.
5 Shift the shift position to D or
R and release the parking
brake. Then, while exercising
caution, depress the acceler-
ator pedal.
■When it is difficult to free the
vehicle
Press the switch to turn off
TRAC.
“Traction Control Turned Off”
If the vehicle becomes
stuck
Carry out the following pro-
cedures if the tires spin or
the vehicle becomes stuck
in mud, dirt or snow:
Recovering procedure
WARNING
■When attempting to free a
stuck vehicle
If you choose to push the vehicle
back and forth to free it, make
sure the surrounding area is clear
to avoid striking other vehicles,
objects or people. The vehicle
may also lunge forward or lunge
back suddenly as it becomes free.
Use extreme caution.
■When shifting the shift posi-
tion
Be careful not to shift the shift
position with the accelerator pedal
depressed.
This may lead to unexpected
rapid acceleration of the vehicle
that may cause an accident
resulting in death o r serious injury.
NOTICE
■To avoid damaging the trans-
mission and other compo-
nents
●Avoid spinning the rear wheels
and depressing the accelerator
pedal more than necessary.
●If the vehicle remains stuck
even after these procedures are
performed, the vehicle may
require towing to be freed.