2010 TOYOTA PRIUS coolant temperature

184 2-2. Instrument cluster
PRIUS_U (OM47668U) U.S.A.
Instrument panel light controlThe brightness of the instrument panel lights can be adjusted.
Brighter
Darker
ITO22P101
NOTICE
■To prevent damage to the hybr id system and its components
The hybrid system may be overheating if the high coolant temperature warn-
ing light comes on. In this case, immediately stop the vehicle in a safe place,
and check the hybrid system after it has cooled completely. ( P. 548)

418 4-3. Do-it-yourself maintenance
PRIUS_U (OM47668U) U.S.A.
CAUTION
The engine 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 engine compartment
● Keep hands, clothing, and tools away from the moving fan.
● Be careful not to touch the engine, power control unit, radiator, exhaust
manifold, etc. right after driving as they may be hot. Oil and other fluids
may also be hot.
● Do not leave anything that may burn easily, such as paper or rags, in the
engine compartment.
● Do not smoke, cause sparks or expose an open flame to fuel. Fuel fumes
are flammable.
● 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 the hybrid system is operating with the “READY” indicator on, the
engine may suddenly start in some cases. When you inspect the engine
compartment, be sure to turn off the hybrid system.
■ When working near the electric cooling fan or radiator grille
Be sure the “POWER” switch is OFF. 
With the “POWER” switch in ON mode, the electric cooling fan may automat-
ically start to run if the air conditioning is on and/or the coolant temperature
is high. ( P. 432)
■ Safety glasses
Wear safety glasses to prevent flying or falling material, fluid spray, etc. from
getting in the eyes.

500 5-2. Steps to take in an emergency
PRIUS_U (OM47668U) U.S.A.
Warning lightWarning light/DetailsCorrection procedure
Tire pressure warning
light
When the light comes on:
Low tire inflation pres-
sure. Adjust the tire
inflation pressure.
When the light comes on
after blinking for 1 minute:
Malfunction in the tire
pressure warning system. Have the system
checked by your
Toyota dealer.
High coolant tempera-
ture warning light
Indicates high engine
coolant temperature P. 5 4 8
Master warning light A buzzer sounds and the
warning light comes on
and flashes to indicate
that the master warning
system has detected a
malfunction. P. 5 0 8

548
5-2. Steps to take in an emergency
PRIUS_U (OM47668U) U.S.A.
If your vehicle overheats
Correction procedures■ If the high coolant temperatur e warning light comes on or
flashes
Stop the vehicle in a safe place and turn off the air condition-
ing system.
Check to see if steam is coming out from under the hood.
If you see steam: 
Stop the hybrid system. Carefully lift the hood after the
steam subsides and then restart the hybrid system.
If you do not see steam: 
Leave the hybrid system operating and carefully lift the
hood.
The following may indicate that your vehicle is overheating:
● The high coolant temperature warn ing light comes on or flashes:
The engine may be overheating.
● “HYBRID SYSTEM OVERHEAT” is shown on the multi-informa-
tion display: 
The power control unit may be overheating.
Follow the correction procedure as described below.
STEP1
STEP2

5
When trouble arises
549
5-2. Steps to take in an emergency
PRIUS_U (OM47668U) U.S.A.
Check to see if the cooling fans are operating.
If the fans are operating: 
Wait until the high coolant temperature warning light goes
off and then stop the hybrid system.
If the fans are not operating:  Stop the hybrid system immedi ately and call your local
Toyota dealer.
After the hybrid system has
cooled down sufficiently, check
the engine coolant level and
inspect the radiator core (radia-
tor) for any leaks.
If necessary, add engine coolant
up to the “FULL” line.
Water can be used in an emer-
gency measure if engine coolant
is unavailable. (P. 562)
STEP3
STEP4
ITO52P130
STEP5

608 Alphabetical index
PRIUS_U (OM47668U) U.S.A.
Vanity lightsVanity lights ...........................377
Wattage .................................567
Vanity mirrors...........................377
Vehicle identification 
number ...................................557
Vehicle load limits.................... 260
Warning buzzers Brake system ........................496
Open door ............................ 499
Seat belt reminder .................499
Warning lights Anti-lock brake 
system (ABS) ......................497
Automatic headlight  leveling system .... ...............497
Brake system ........................496
Charging system .... ...............497
Electric power steering .........497
High coolant temperature ......499
Low fuel level ........................499
Malfunction indicator lamp ....497
Master warning......................499
Open door ............................. 499
Pre-Collision system ............. 497
Seat belt reminder .................499
SRS airbags .......................... 497
Tire pressure .........................499
Warning messages .................. 508
Washer Checking ............................... 434
Preparing and checking 
before winter ....................... 261
Switch.................................... 210
Washing and waxing ............... 404 Weight
Cargo capacity ...................... 260
Load limits ............................. 260
Weight ................................... 556
Wheels ...................................... 455
Window glasses ........................ 98
Window lock switch................... 98
Windows Power windows ....................... 98
Rear window defogger .......... 289
Washer.................................. 210
Windshield wipers ................... 210
Winter driving tips ................... 261
Wireless remote control key Locking/Unlocking ................... 63
Replacing the battery ............ 460
WMA disc.................................. 311V
W

610
PRIUS_U (OM47668U) U.S.A.
What to do if...
What to do if...
A tire puncturesP. 524If you have a flat tire
The hybrid system does not start
P. 108Immobilizer system
P. 538If the hybrid system will not start
P. 543If the 12 volt battery is discharged
The high coolant temperature
warning light comes on
Steam can be seen coming 
from under the hood
P. 548If your vehicle overheats
The key is lostP. 540If you lose your keys
The 12 volt battery runs outP. 543If the 12 volt battery is discharged
The doors cannot be lockedP. 6 7Side doors
P. 7 2Back door
The vehicle is stuck in mud or
sandP. 553If the vehicle becomes stuck

612 What to do if...
PRIUS_U (OM47668U) U.S.A.
■Warning lights
P. 4 V VP. 497
P. 4 V T
or
P. 497
or
P. 4 V TP. 499
P. 497
or
P. 4 V SP. 497
P. 499
P. 4 V T
P. 499
P. 4 V T
P. 499
P. 4 V V
P. 499
Master warning lightSRS warning light
Charging system 
warning lightABS warning light
Malfunction indicator
lamp
Tire pressure warning
light
Brake system warning
light (red indicator)Electric power steering
warning light
Pre-collision system
warning light
High coolant temperature
warning light
Low fuel level warning
light
Automatic headlight 
leveling system 
warning light
Driver’s seat belt reminder 
light
Open door warning light
Brake system warning
light (yellow indicator) Brake system warning
light (yellow indicator) Brake system warning
light (yellow indicator)
Front passenger’s seat
belt reminder light