coolant temperature TOYOTA MIRAI 2023 Owners Manual

822-1. Fuel cell electric vehicle
Owners Manual_USA_M62064_en
■High-voltage and high-temperature components
The fuel cell electric vehicle has high-voltage components (abo ut
650 V maximum) such as a fuel c ell stack, traction battery, power
control unit, fuel cell converter, high-voltage cables (which a re distin-
guished from low-voltage cables b y their orange covers), electric
motor (traction motor), etc., and high-temperature parts such a s the
radiator for cooling. Pay attention to all warning labels attached to
the vehicle.
This diagram is for illustrative purposes only and may differ f rom the actual
vehicle.
Warning label
Radiator for inverter cooling
Radiator for fuel cell stack cooling
Fuel cell water pump
Fuel cell converter and auxiliary inverter
Power control unit
Cabin coolant heater
Traction battery
Service plug

842-1. Fuel cell electric vehicle
Owners Manual_USA_M62064_enhydrogen tanks or valves need to
be disposed.
■Fuel cell stack coolant
●Fuel cell stack coolant uses a spe-
cifically-designed fluid with high
electrical insulation properties, in
order to safely cool the high-volt-
age fuel cell stack.
●Never add water or other coolants
to the fuel cell st
ack cooling sys-
tem, as they will cause permanent
damage.
●Consult your Toyota dealer for
replenishing or changing the fuel
cell stack coolant.
■Ion filter
●An ion filter is inst alled in the cool-
ant lines for the fuel cell stack, in
order to maintain the normal insu-
lation properties of the coolant.
●It is necessary to periodically
change the ion filter. ( P.466)
Contact your Toyota dealer for this
periodic maintenance.
■Tailpipe
●When the power switch is turned
off and the fuel cell system is
stopped ( P.182) after driving,
exhaust water is discharged. Be
careful when standing behind the
vehicle to avoid dripping or spray-
ing.
●It is possible to manually purge
the exhaust. Thi s may be desir-
able, for instance, before parking
in a garage. This is done by press-
ing the H
2O switch. ( P.196)
●On cold days, water vapor in the
exhaust may appe ar as a white
mist emitted from the tailpipe. This
is not a malfunction. A white mist
may be emitted from the vehicle
side depending on the wind direc-
tion. If it is a concern, consult with
a Toyota dealer.
●If the tailpipe is blocked, the fuel
cell system will stop.
●In the following state when cold, a white mist may be emitted. Water
vapor is being emitted as a sys-
tem protection and it is not a mal-
function.
• If several minutes have passed after opening the fuel lid, such as
refueling.
• Several hours have passed after the power switch was turned off.
■Hydrogen detectors
When the power switch is turned to
ON, the hydrogen detectors are
activated.
■Power output restriction
When the power output is restricted,
the vehicle may fa il to accelerate or
even decelerate, even though the
accelerator pedal is depressed. If a
safe driving speed cannot be main-
tained, stop the ve hicle in a safe
place away from the traffic. This
may be caused by the following con-
ditions:
●The coolant temperature may be
too high. This can be caused by
driving conditions such as
repeated sudden acceleration and
deceleration, continuous driving
on an incline, continuous driving
at high altitudes with a high load,
etc. In such situations, “FCV sys-
tem overheated Output power
reduced” is displayed on the multi-
information display, and the power
output is restricted. Once the cool-
ant returns to normal temperature,
the power output will retu rn to nor-
mal. ( P.464)
●The remaining fuel may be low.
After the low fuel level warning
light comes on, the output power
will be gradually restricted in order
to extend the possible driving dis-
tance. Once getting to this point,
the remaining driving distance
possible is short. Immediately refill
the vehicle with hydrogen.
●On cold days, the low fuel level
warning light comes on faster than
usual and the output power is
restricted.

963-1. Instrument cluster
Owners Manual_USA_M62064_en
*1: These lights turn on when the power switch is turned to ON to
indicate that a system check is
being performed. They will turn
off after the fuel cell system is
on, or after a few seconds. There
may be a malfunction in a sys-
tem if the light does not come on,
or turn off. Have the vehicle
inspected by your Toyota dealer.
*2: This light illuminates on the multi-informatio n display with a
message.
*3: Intuitive parking assist OFF indi- cator turns on when the power
switch is turned to ON while the
Intuitive parking assist function is
on. It will turn off after a few sec-
onds.
*4: Refer to “Toyota Teammate Advanced Drive OWNER’S
MANUAL” at Toyota.com.
(Canada)
(Flashes)
Parking brake indica-
tor ( P.459)
Tire pressure warning
light
*1 (  P.460)
Low fuel level warn-
ing light ( P.460)
Driver’s and front pas-
senger’s seat belt
reminder light
(  P.460)
Rear passengers’ seat
belt reminder lights
(  P.461)
Advanced Drive warn-
ing light (if
equipped)
*1, 4
WARNING
■If a safety system warning
light does not come on
Should a safety system light such
as the ABS and SRS warning light
not come on when you start the
fuel cell system, this could mean
that these system s are not avail-
able to help protect you in an acci-
dent, which could result in death
or serious injury. Have the vehicle
inspected by you r Toyota dealer
immediately if this occurs.
NOTICE
■To prevent damage to the fuel
cell system and its compo-
nents
This vehicle is equipped with high
coolant temperature warning light
(  P.490), instead of, coolant tem-
perature gauge.
The fuel cell sys tem may be over-
heating if the high coolant tem-
perature warning light flashes or
comes on. In this case, immedi-
ately stop the vehicle in a safe
place, and check the fuel cell sys-
tem after it has cooled completely.

973-1. Instrument cluster
Owners Manual_USA_M62064_en
3
Vehicle status information and indicators
The indicators inform the driver
of the operating state of the
vehicle’s various systems.
Indicators
Turn signal indicator
(  P.190)
(U.S.A.)
Headlight indicator
( P.198)
(Canada)
Tail light indicator
( P.198)
Headlight high beam indi-
cator ( P.200)
AHB indicator ( P.200)
(Blue)
Low coolant temperature
indicator
*1
Smart key system indica-
tor
*2 ( P.180)
Cruise control indicator
(  P.244)
Dynamic radar cruise
control indicator
(  P.244)
Cruise control “SET” indi-
cator ( P.244)
(*3)
LTA indicator ( P.220,
236)
Intuitive parking assist
OFF indicator
*4, 5 (if
equipped) ( P.262)
PKSB OFF indicator
*4, 6
(if equipped) ( P.283)
(Flashes)
Slip indicator light*6
(  P.323)
VSC OFF indicator
*4, 6
(  P.323)
PCS warning light
*4, 6
(  P.222)
BSM outside rear view
mirror indicators
*6, 7 (if
equipped) ( P.257, 272)
BSM OFF indicator
*4, 6 (if
equipped) ( P.257)
RCTA OFF indicator
*4, 6
(if equipped) ( P.273)
RCD OFF indicator
*4 (if
equipped) ( P.278)
Brake hold standby indi-
cator
*6 (  P.194)
Brake hold operated indi-
cator
*6 (  P.194)
Security indicator
*8
(  P.70, 71)
“READY” indicator
(  P.180)
Low outside temperature
indicator
*9 (  P.100)
(U.S.A.)
Parking brake indicator
( P.191)
(Canada)
Parking brake indicator
( P.191)
Br mode indicator
(  P.185)
Eco drive mode indicator
(  P.320)

983-1. Instrument cluster
Owners Manual_USA_M62064_en
*1: Indicates the coolant tempera-ture is cool.
*2: This light illuminates on the multi-informatio n display with a
message.
*3: Depending on the operating con- ditions of the system, the color
and state (illuminated/blinking) of
the indicator change.
*4: The light comes on when the system is turned off.
*5: Intuitive parking assist OFF indi-cator turns on when the power
switch is turned to ON while the
Intuitive parking assist function is
on. It will turn off a fter a few sec-
onds.
*6: These lights turn on when the power switch is turned to ON to
indicate that a system check is
being performed. They will turn
off after the fuel cell system is
on, or after a few seconds. There
may be a malfunction in a sys-
tem if the lights do not turn on, or
turn off. Have the vehicle
inspected by your Toyota dealer.
*7: This light illumi nates on the out-
side rear view mirrors.
*8: This light illumi nates on the cen-
ter panel.
*9: When the outside temperature is approximately 37°F (3°C) or
lower, the indicator will flash for
approximately 10 seconds, then
stay on.
*10: Refer to “Toyota Teammate Advanced Drive OWNER’S
MANUAL” at Toyota.com.
Sport mode indicator
(
 P.320)
Snow mode indicator
(  P.321)
“AIRBAG ON/OFF” indi-
cator
*6, 8 (  P. 4 6 )
Advanced Drive indica-
tor
*10 (if equipped)

4057-3. Do-it-yourself maintenance
Owners Manual_USA_M62064_en
7
Maintenance and care
Tire inflation
pressure
(  P.428)• Tire pressure
gauge
• Compressed air source
Washer fluid
( P.412)
• Water or washer
fluid containing
antifreeze (for
winter use)
• Funnel (used only for adding
water or washer
fluid)
WARNING
The fuel cell unit compartment
contains many mechanisms and
fluids that may move suddenly,
become hot, or become electri-
cally energized. To avoid death or
serious injury, observe the follow-
ing precautions.
■When working on the fuel cell
unit compartment
●Be careful not to touch the high-
voltage parts or hydrogen-
related parts.
●Make sure that the “READY”
indicator is off.
●Keep hands, clothing and tools
away from the moving fan.
●Be careful not to touch the
motor, inverter, radiator, etc.
right 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
rags, in the fuel cell unit com-
partment.
ItemsParts and tools●Do not smoke, cause sparks or
expose an open flame to the 12-
volt battery. 12-volt battery
fumes are flammable.
●Be extremely cautious when
working on the 12-volt battery. It
contains poisonous and corro-
sive sulfuric acid.
●Take care because brake fluid
can harm your hands or eyes
and damage painted surfaces. If
fluid gets on your hands or in
your eyes, flush the affected
area with clean water immedi-
ately.
If you still experience discom-
fort, consult a doctor.
●Never touch, disassemble,
remove or replace the high-volt-
age parts, cables and their con-
nectors. It can cause severe
burns or electric shock that may
result in death or serious injury.
■When working near the elec-
tric cooling fan or radiator
grille
Be sure the power switch is off.
With the power switch in ON, the
electric cooling fa n may automati-
cally start to run if the air condi-
tioning is on and/or the coolant
temperature is high. ( P. 4 1 1 )
■Safety glasses
Wear safety glasses to prevent
flying or falling material, fluid
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.

4538-2. Steps to take in an emergency
Owners Manual_USA_M62064_en
8
When trouble arises
 Fluid leaks under the vehicle.
(Water dripping from the air
conditioning after use is nor-
mal.)
 Flat-looking tires or uneven
tire wear
 The high coolant temperature
gauge needle continually
points higher than normal.
 Hydrogen gas leakage noises
can be heard. ( P.87)
 Excessive tire squeal when
cornering
 Strange noises related to the
suspension system
 Other noises related to the
fuel cell system 
Stumbling or running roughly
 Appreciable loss of power
 Vehicle pulls heavily to one
side when braking
 Vehicle pulls heavily to one
side when driving on a level
road
 Loss of brake effectiveness,
spongy feeling, pedal almost
touches the floor
If you think something
is wrong
If you notice any of the fol-
lowing symptoms, your
vehicle probably needs
adjustment or repair. Con-
tact your Toyota dealer as
soon as possible.
Visible symptoms
Audible symptoms
Operational symptoms

4558-2. Steps to take in an emergency
Owners Manual_USA_M62064_en
8
When trouble arises
■High coolant temperature warning light
■Fuel cell system overheat warning light* (warning buzzer)
*: This light illuminates on the mu lti-information display with a message.
■Charging system warning light* (warning buzzer)
*: This light illuminates on the mu lti-information display with a message.
■SRS warning light
■Pop Up Hood warning light
Warning lightDetails/Actions
(Red)
Indicates that the coolant temperature is too high
 Immediately stop the v ehicle in a safe place.
Handling method ( P.490)
Warning lightDetails/Actions
Indicates the fuel cell system has overheated
 Stop the vehicle in a safe place.
Handling method ( P.490)
Warning lightDetails/Actions
Indicates a malfunction in t he vehicle’s charging system
 Immediately stop the vehicle in a safe place and con-
tact your Toyota dealer.
Warning lightDetails/Actions
Indicates a malfunction in:
The SRS airbag system;
 The front passenger occupant classification system; or
 The seat belt pretensioner system
 Have the vehicle inspecte d by your Toyota dealer
immediately.
Warning lightDetails/Actions
Indicates that the Pop Up Hood system has operated
 The Pop Up Hood system can not be reused once it
has operated. Have it replaced by your Toyota dealer.
Indicates a malfunction in the Pop Up Hood system
 Have the vehicle inspecte d by your Toyota dealer
immediately.

4908-2. Steps to take in an emergency
Owners Manual_USA_M62064_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.455) 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.455) comes on
 Steam comes out from under the hood.
Parts name for cooling components

4938-2. Steps to take in an emergency
Owners Manual_USA_M62064_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.