engine overheat Lexus GS450h 2007 Scheduled Maintenance Guide / LEXUS 2007 GS450H FROM JULY 2006 PROD. OWNER'S MANUAL (OM30A05U)

99
2-1. Driving procedures
2
When driving
CAUTION
■When driving the vehicle
●Do not under any circumstances shift the shift lever to “P”, “R” or “N” while the
vehicle is moving.
Doing so can cause significant damage to the transmission and may result in a
loss of vehicle control.
●Do not shift the shift lever to “N” while the vehicle is moving. 
Doing so may cause the engine brake not to operate properly and lead to an
accident.
●Do not turn the hybrid system off while driving. 
The brake actuator will not operate properly if the hybrid system is off.
●Use engine braking (downshift) to maintain a safe speed when driving down a
steep hill. 
Using the brakes continuously may cause the brakes to overheat and lose effec-
tiveness. ( P. 1 0 8 )
●When stopped on an inclined surface, use the brake pedal and parking brake to
prevent the vehicle from rolling backward or forward and causing an accident.
●Be careful when driving on slippery surfaces, as the vehicle may spin or skid when
downshifting, rapidly accelerating, braking or turning.
●Do not adjust the position of the steering wheel, the seat, or the inside or outside
rear view mirrors while driving. 
Doing so may result in a loss of vehicle control that can cause accidents that may
result in death or serious injury.
●Always check that all passengers' arms, heads or other parts of their bodies are
not outside the vehicle, as this may result in death or serious injury.

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2-2. Instrument cluster
2
When driving
NOTICE
■To prevent damage to the engine and its components
The engine may be overheating if the engine coolant temperature gauge is in the
red zone (“H”). In this case, immediately stop the vehicle in a safe place. Check the
engine after it has cooled completely. ( P. 4 8 0 )
■To activate the light sensitivity function properly
Do not affix a sticker or window tint to the rear window glass, or put an object
behind the rear seat.

480
5-2. Steps to take in an emergency
If your vehicle overheats
■Electric motor (traction motor) and inverter
If the message “HYBRID SYSTEM OVERHEAT” is displayed on the
multi-information display.
■ Gasoline engine
If the needle of the engine co olant temperature gauge enters the
red zone, the gasoline engine has probably overheated.
Observe the following steps:
Stop the vehicle in a safe place and turn off the automatic air
conditioning system.
Check to see if steam is coming out from under the hood.
If you see steam: 
Stop the hybrid system and carefully lift the hood.
If you do not see steam: Leave the hybrid system running and carefully lift the hood.
Remove the engine compartment cover. ( P. 370)
Check to see if the cooling fan is operating.
If the fan is operating: 
Wait until the engine coolant temperature gauge begins to
fall and then stop the hybrid system.
If the fan is not operating: 
Stop the hybrid system immed iately and call your local
Lexus dealer.
After the hybrid system has
cooled down sufficiently, check
the coolant level and inspect the
radiator core (radiator) for any
leaks.
STEP1
STEP2
STEP3
STEP4
STEP5

5
When trouble arises
481
5-2. Steps to take in an emergency
■Overheating
In the following situations, your vehicle may be overheating.
●The message “HYBRID SYSTEM OVERHEAT” is displayed on the multi-infor-
mation display.
●The engine coolant temperature gauge enters the red zone or a loss of power is
experienced.
●Steam is coming from under the hood.
CAUTION
■To prevent an accident or injury when in specting under the hood of your vehicle
●Keep hands and clothing away from the fan and engine drive belt while the hybrid
system is running.
●Do not loosen the radiator cap while the hybrid system and radiator are hot. 
Serious injury, such as burns, may resu lt from hot coolant and steam released
under pressure.
Add coolant if required.
Water can be used in an emer-
gency measure if coolant is
unavailable. ( P. 4 9 0 )
Have the vehicle checked at your nearest Lexus dealer as soon as pos-
sible.
STEP6

519
Alphabetical index
Installing CRS with lower 
anchorages .......................................... 89
Installing CRS with seatbelts .......... 85
Installing CRS with top straps ........ 90
Child safety Airbag precautions .............................. 72
Child restraint system ........................ 82
Child-protectors....................................26
How your child should wear 
the seatbelt ............................................43
Installing child restraints .................... 85
Moon roof ................................................ 54
Power window lock switch ............. 50
Power window precautions.............. 51
Removed electronic key battery 
precautions ....................................... 402
Seat belt comfort guide....................... 41
Seat belt precautions...........................44
Seat heater precautions .........319, 321
Trunk............................................................32
Cigarette lighter ..................................... 317
Cleaning Exterior ................................................... 352
Interior..................................................... 354
Seat belts ............................................... 355
Clock........................................................... 314
Coin holder ............................................ 309
Compass ................................................. 334
Condenser............................................... 377
Console box........................................... 307
Cooling system Engine overheating ..........................480 Cruise control
Cruise control........................................129
Dynamic radar cruise control........132
Cup holders ............................................. 310
Curtain shield airbags............................ 66
Customizable features ........................ 510
Daytime running light system ........... 123
Defogger Rear window ......................................... 199
Side mirror.............................................. 199
Dimension................................................486
Dinghy towing ......................................... 182
Display Energy flow ................................................. 6
Multi-information display .................. 119
Touch screen ........................................ 184
Trip information ................................... 120
Warning message ............................. 444
Do-it-yourself maintenance .............363
Door courtesy lights ............................304
Door pocket............................................... 311
Doors Door lock .................................................. 25
Rear door child protector ................ 26
Driver's seat belt reminder light .....440
Driving Correct posture..................................... 64
Procedures ..............................................96
DVD player/changer.......................... 232
Electronic key Replacing battery................................ 401
When the electronic key battery 
is discharged..................................... 474
D
E

520
Alphabetical index
Emergency, in case ofIf a warning light turns on ..............438
If a warning message is 
displayed ............................................ 444
If the hybrid system will not 
start.......................................................... 471
If the shift lever cannot be  shifted from P ....................................472
If the 12 volt battery is 
discharged ....................................... 476
If you have a flat tire .............. 460, 461
If you lose your keys......................... 473
If you think something is 
wrong ................................................... 435
If your vehicle becomes stuck.....483
If your vehicle needs to be 
towed ................................................... 428
If your vehicle overheats ............... 480
When the electronic key battery 
is discharged .................................... 474
Energy monitor............................................ 6
Engine Compartment .....................................369
Hood........................................................366
How to start the hybrid system ... 103
If the hybrid system will not 
start.......................................................... 471
Overheating........................................ 480
Power switch ........................................ 103
Engine compartment cover .............370
Engine coolant temperature 
gauge......................................................... 112
Engine/inverter coolant Capacity .................................................490
Checking ............................................... 376
Preparing and checking before winter ...................................... 176 Engine oil
Capacity ................................................ 489
Checking................................................. 371
Preparing and checking 
before winter...................................... 176
Engine oil maintenance data ........... 374
EPS (Electric Power Steering) .........164
Event data recorder ............................ 436
First-aid kit storage belt ..................... 327
Floor mats ................................................ 326
Fluid Brake ....................................................... 378
Washer................................................... 382
Fog lights Switch ........................................................ 125
Wattage ................................................. 494
Foot light .................................................. 304
Front passenger occupant 
classification system ............................. 77
Front passenger's seat belt 
reminder light ..................................... 440
Front seats Adjustment ...............................................33
Driving position memory ..................35
Front turn signal lights Wattage ................................................. 494
Fuel Capacity ................................................ 488
Fuel gauge ................................................ 112
Gas station information ................. 528
Information ........................................... 495
Refueling ................................................... 55
Messages .............................................. 456
Fuel filler door ........................................... 55
Fuses .......................................................... 403
F

522
Alphabetical index
Replacing light bulbs.......................... 421
Turn signal lever .................................... 110
Vanity lights ............................................313
Wattage.................................................. 494
Maintenance Do-it-yourself maintenance ......... 363
General maintenance .....................359
Maintenance data..............................486
Maintenance requirements .......... 357
Meter Instrument panel light control .........113
Meters .........................................................112
Micro dust and pollen removal 
mode ........................................................ 195
Mirrors Inside rear view mirror........................47
Side mirror heater ...............................199
Side mirrors ............................................. 48
Vanity mirrors........................................313
Moon roof ................................................... 52
MP3 disc ...................................................... 224
Multi-information display ....................... 119
Odometer................................................... 112
Oil Engine oil ................................................. 371
Opener Fuel filler door......................................... 55
Hood........................................................366
Trunk ........................................................... 29
Outside rear view mirrors Adjusting and folding ......................... 48
Driving position memory.................. 35
Outside temperature display............ 315
Overhead console .............................. 308 Overheating, Engine
............................. 480
Parking brake..............................................111
Parking lights Replacing light bulbs ......................... 421
Switch .........................................................122
Wattage ................................................. 494
PCS (Pre-Collision System) ..............165
Personal lights........................................305
Power meter.............................................. 112
Power outlet ............................................ 318
Power windows ........................................ 50
Radar cruise control..............................132
Radiator .....................................................377
Radio .............................................................. 203
RDS (Radio Data System) ................ 205
Rear sunshade ....................................... 324
Rear turn signal lights Replacing light bulbs ......................... 421
Wattage ................................................. 494
Rear view monitor system ................. 160
Rear window defogger ........................199
Replacing Electronic key battery ....................... 401
Fuses ........................................................ 403
Light bulbs .............................................. 421
Reporting safety defects for 
U.S. owners............................................516
Seat belts Adjusting the seat belt ..........................41
Automatic Locking Retractor 
(ALR) ....................................................... 42
Child restraint system 
installation ............................................. 85
M
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What to do if...
What to do if...
A tire puncturesP. 4 6 0 /461If you have a flat tire
The hybrid system does not start
P. 5 9Hybrid vehicle immobilizer system
P. 4 7 1If the hybrid system will not start
P. 4 76If the 12 volt battery is discharged
The shift lever cannot be 
moved outP. 4 7 2If the shift lever cannot be shifted 
from “P”
The engine coolant temperature
gauge enters the red zone
Steam can be seen coming 
from under the hood
P. 4 8 0If your vehicle overheats
The key is lostP. 4 7 3If you lose your keys
The battery runs outP. 4 76If the 12 volt battery is discharged
The doors cannot be lockedP. 2 5Doors
The horn begins to soundP. 6 1Alarm
The vehicle is stuck in mud or
sandP. 4 8 3If the vehicle becomes stuck