cooling TOYOTA MIRAI 2018 Owners Manual (in English)

832. Fuel cell vehicle
2
Fuel cell system
MIRAI_OM_USA_OM62025U
The fuel cell vehicle has high-voltage components (about 650 V m axi-
mum) such as a fuel cell stack, traction battery, power control unit,
high-voltage cables (which are di stinguished from low-voltage cables
by their orange covers), electric motor (traction motor), etc., and high-
temperature parts such as the radiator for cooling. Pay attenti on to all
warning labels attached to the vehicle.
This diagram is for illustrative purposes only and may differ f rom the
actual vehicle.
High-voltage and high-temperature components
Warning label
Power control unit
High-voltage cables (orange)
Fuel cell stack
Traction battery
Service plug
Fuel cell converter Electric motor (traction motor)
Air conditioning compressor
Radiator for inverter cooling
Radiator for fuel cell stack
cooling
Auxiliary inverter
Cabin coolant heater

852. Fuel cell vehicle
2
Fuel cell system
MIRAI_OM_USA_OM62025U
There is an air intake vent beside
the rear left seat for the purpose
of cooling the traction battery. If
the air intake vent is blocked, it
could lead to a reduction in trac-
tion battery output.
■If a warning light comes on, a warning message is displayed, or the
12-volt battery connection is disconnected
The fuel cell system may not be able to restart.
If the “READY” indicator does not come on, even when the start procedure is
repeated, contact your Toyota dealer.
■ If “Hydrogen Leakage Detected Visit Your Dealer” is displayed on the
multi-information display
A small amount of hydrogen gas may be leaking. Have the vehicle inspected
immediately at the nearest Toyota dealer.
■ If “FC System Shutdown due to Hydrogen Leakage Stop Your Vehicle in
a Safe Place and Contact Your Dealer” is displayed on the multi -informa-
tion display
● Hydrogen gas may be leaking.
When hydrogen gas is leaking or some other malfunction is detected:
P. 90
● The air conditioning system will shut off automatically.
■ Running out of fuel
When the vehicle has run out of fuel and the fuel cell system c annot be
started, refuel the vehicle until the low fuel level warning li ght (P. 371) turns
off before trying to restart. It may not be able to restart if the refueled amount
is too low (less than about 2.7 lb. [1.2 kg]).
Traction battery air intake vent

2586-1. Using the air conditioning system and defogger
MIRAI_OM_USA_OM62025U
Touch .
The dehumidification function begi ns to operate. Air outlets and fan
speed are automatically adjusted according to the temperature s et-
ting.
Adjust the temperature setting.
Touch .
The cooling and dehumidificati on function switches between on a nd
off each time is touched.
To stop the operation, touch .
■Automatic mode indicator
If the fan speed setting or air flow modes are operated, the au to-
matic mode indicator goes off. However, automatic mode for func -
tions other than that o perated are maintained.
■Switching between outside air and recirculated air modes
Press .
The mode switches between outside air mode (indicator off) and recir-
culated air mode (indicator on) each time is pressed.
■
Using the ECO HEAT/COOL mode
Touch .
is displayed on the air conditioning screen, and the air condi tion-
ing is controlled with low fuel consumption prioritized. When is
touched and held, is displayed on the screen, and the air cond i-
tioning is controlled, even more, with low fuel consumption pri oritized.
(The air conditioning will have more reserved operation.)
When canceling ECO HEAT/COOL mode, touch the again.
may be canceled when other air conditioning operation switches
are touched.
Using the automatic air conditioning system
Other functions

2616-1. Using the air conditioning system and defogger
6
Interior features
MIRAI_OM_USA_OM62025U■
Fogging up of the windows
●The windows will easily fog up when the humidity in the vehicle is high.
Turning on will dehumidify the air from the outlets and defog the wind-
shield effectively.
● If you turn off, the windows may fog up more easily.
● The windows may fog up if the recirculated air mode is used.
■ Windshield fog detection function
When automatic mode is set, the humidity sensor ( P. 264) detects fog on
the windshield and controls the air conditioning system to prev ent fog.
■ Outside/recirculated air mode
●When driving on dusty roads such as tunnels or in heavy traffic, set the out-
side/recirculated air mode button to recirculated air mode. Thi s is effective in
preventing outside air from entering the vehicle interior. Duri ng cooling oper-
ation, setting the recirculated air mode will also cool the vehicle interior
effectively.
● Outside/recirculated air mode may automatically switch dependin g on the
temperature setting or the inside temperature.
■ Operation of the air conditioni ng system in ECO HEAT/COOL mode
● In ECO HEAT/COOL mode, the air conditioning system is controlle d as fol-
lows to prioritize fuel efficiency:
• Fluid (heating) heater and compressor operation controlled to restrict
heating/cooling capacity
• Fan speed restricted when automatic mode is selected
● To improve air conditioning performance, perform the following operations:
• Adjust the temperature settings and fan speed
• Touch while in , and is set
• Touch while in , and ECO HEAT/COOL mode is canceled
■ Operation of the air conditioning system in Eco drive mode
When ECO MODE switch is pressed, operations switch over to ECO HEAT/
COOL mode. ( P. 183)
■ When the outside temperature exceeds 75°F (24°C) and the air co ndition-
ing system is on
● In order to reduce the air conditioning power consumption, the air condition-
ing system may switch to recirculated air mode automatically. This may also
reduce fuel consumption.
● Recirculated air mode is selected as a default mode when the power switch
is turned to ON mode.
● It is possible to switch to outside air mode at any time by pre ssing .

3197-3. Do-it-yourself maintenance
MIRAI_OM_USA_OM62025U
7
Maintenance and care
WARNING
The motor compartment contains many mechanisms and fluids that may
move suddenly, become hot, or become electrically energized. To avoid death
or serious injury, observe the following precautions.
■ When working on the motor compartment
● Be careful not to touch the high-voltage parts or hydrogen-rela ted parts.
● Make sure that the “READY” indicator is off.
● Keep hands, clothing and tools away from the moving fans.
● Be careful not to touch the motor, inverter, radiator, etc., ri ght after driving
as they may be hot. Coolant and other fluids may also be hot.
● Do not leave anything that may burn easily, such as paper and r ags, in the
motor compartment.
● Do not smoke, cause sparks or expose an open flame to the 12-volt bat-
tery. 12-volt battery fumes are flammable.
● Be extremely cautious when working on the 12-volt battery. It c ontains poi-
sonous and corrosive sulfuric acid.
● Take care because brake fluid can harm your hands or eyes and d amage
painted surfaces. If fluid gets on your hands or in your eyes, flush the
affected area with clean water immediately.
If you still experience discomfort, consult a doctor.
● Never touch, disassemble, remove or replace the high-voltage parts,
cables and their connectors. It can cause severe burns or electric shock
that may result in death or serious injury.
■ When working near the electric cooling fans or radiator grille
Be sure the power switch is off.
With the power switch in ON mode, the electric cooling fans may automati-
cally start to run if the air conditioning is on and/or the coolant temperature
is high. ( P. 325)
■ Safety glasses
Wear safety glasses to prevent flying or falling material, flui d spray, etc.,
from getting in your eyes.
NOTICE
■ If you remove the air cleaner filter
Driving with the air cleaner filter removed may cause excessive motor wear
due to dirt in the air.

3237-3. Do-it-yourself maintenance
MIRAI_OM_USA_OM62025U
7
Maintenance and care
Motor compartment
Washer fluid tank (P. 327)
Brake fluid reservoir ( P. 326)
Inverter coolant reservoir ( P. 324)
Fuse boxes ( P. 355)
Fuel cell stack coolant radiator
( P. 325) Inverter coolant radiator
( P. 325)
Condenser ( P. 325)
Electric cooling fans
Fuel cell stack coolant reser-
voir ( P. 324)
Fuel cell stack coolant sub
radiator ( P. 325)

3257-3. Do-it-yourself maintenance
MIRAI_OM_USA_OM62025U
7
Maintenance and care
■If the inverter coolant level drops within a short time of repl enishing
Visually check the radiators, hoses, inverter coolant reservoir cap, drain cock
and water pump.
If you cannot find a leak, have your Toyota dealer test the cap and check for
leaks in the cooling system.
Check the radiator and condenser and clear away any foreign objects.
If either of the above parts is extremely dirty or you are not sure of
their condition, have your vehic le inspected by your Toyota dea ler.
WARNING
■When the fuel cell system is hot
Do not remove the coolant reservoir caps.
The cooling system may be under pressure and may spray hot coolant if the
cap is removed, causing serious injuries, such as burns.
NOTICE
■When adding coolant
Coolant is neither plain water nor straight antifreeze. The cor rect mixture of
water and antifreeze must be used to provide proper lubrication , corrosion
protection and cooling. Be sure to read the antifreeze or coolant label.
■ If you spill coolant
Be sure to wash it off with water to prevent it from damaging p arts or paint.
Radiator and condenser
WARNING
■When the fuel cell system is hot
Do not touch the radiator or condenser as they may be hot and c ause seri-
ous injuries, such as burns.

3778-2. Steps to take in an emergency
MIRAI_OM_USA_OM62025U
8
When trouble arises
*: A buzzer sounds the first time a message is shown on the multi-informa-
tion display.
■ System warning lights
The master warning light does not come on or flash in the following cases.
Instead, a separate system warning light will come on along wit h a message
shown on the multi-information display.
● Malfunction of the ABS
The ABS warning light comes on. ( P. 370)
● Malfunction of the charging system
The charging system warning light comes on. ( P. 3 6 9 )
■ If “High FC Temperature Reduced Power” is displayed
Lower the speed while check the safety, and run the vehicle like this for
several minutes.
If the message goes off, the vehicle can be driven as is, since it temporarily
overheated.
This message may be displayed when driving under severe operati ng con-
ditions.
(For example, when driving up a long steep hill.)
■ If “FC System Shutdown due to F reezing conditions Stop Your Veh icle in
a Safe Place and Contact Your Dealer” is displayed.
The fuel cell system is frozen and can not be started. Contact a Toyota
dealer.
■ If “Maintenance Required for Hybrid Battery Cooling Parts at Yo ur
Dealer” is displayed
The filter may be clogged, the air intake vent may be blocked or there may be
a gap in the duct. Have maintenance performed on the traction b attery cool-
ing component at your Toyota dealer.
Comes onDoes not sound
Indicates a condition, such as mal-
function of electrical components,
their condition, or indicates the
need for maintenance
FlashesDoes not sound
Indicates a situation, such as
when an operation has been per-
formed incorrectly, or indicates
how to perform an operation cor-
rectly
System
warning
light
Warning buzzer*Warning

4058-2. Steps to take in an emergency
MIRAI_OM_USA_OM62025U
8
When trouble arises
WARNING
■12-volt battery precautions
The 12-volt battery contains poisonous and corrosive acidic ele ctrolyte,
while related parts contain lead and lead compounds. Observe th e following
precautions when handling the 12-volt battery:
● When working with the 12-volt battery, always wear safety glass es and
take care not to allow any 12-volt battery fluids (acid) to come into contact
with skin, clothing or the vehicle body.
● Do not lean over the 12-volt battery.
● In the event that 12-volt battery fluid comes into contact with the skin or
eyes, immediately wash the affected area with water and seek me dical
attention.
Place a wet sponge or cloth over the affected area until medica l attention
can be received.
● Always wash your hands after handling the 12-volt battery suppo rt, termi-
nals, and other battery-related parts.
● Do not allow children near the 12-volt battery.
■ After recharging the 12-volt battery
Have the 12-volt battery inspected at your Toyota dealer as soo n as possi-
ble.
If the 12-volt battery is deteriorating, continued use may caus e the 12-volt
battery to emit a malodorous gas, which may be detrimental to the health of
passengers.
■ When exchanging the 12-volt battery
After exchanging, securely attach the exhaust hose and exhaust hole plug
to the exhaust hole of the exchanged 12-volt battery. If not pr operly
installed, gases (hydrogen) may leak into the vehicle interior, and there is
the possible danger of the gas igniting and exploding.
■ When replacing the 12-volt battery
 P. 330
NOTICE
■To prevent damaging the vehicle
The exclusive jump starting terminal is to be used when chargin g the 12-volt
battery from another vehicle in an emergency. It cannot be used to jump
start another vehicle.
■ When handling jumper cables
When connecting the jumper cables, ensure that they do not beco me entan-
gled in the cooling fans.

4078-2. Steps to take in an emergency
MIRAI_OM_USA_OM62025U
8
When trouble arises
■If the high coolant temperature warning light comes on or
flashes
Stop the vehicle in a safe place and turn off the air conditioning sys-
tem, and then stop t he fuel cell system.
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.
After the fuel cell system has
cooled down sufficiently,
inspect the hoses and radiator
core (radiator) for any leaks.
Fuel cell stack coolant sub
radiator
Fuel cell stack coolant radia-
tor
Electric cooling fans
If a large amount of coolant
leaks, immediately contact your
Toyota dealer.
NOTICE
Correction procedures
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, imme-
diately contact your Toyota dealer.