2010 Lexus GS450h engine overheat

144
2-1. Driving procedures
GS_HV_U (OM30C81U)
October 13, 2015 12:41 pm
CAUTION
■When driving the vehicle
●Moving the shift lever to "N" while the vehicle is moving will disengage the hybrid
system. Engine braking is not available with the hybrid system disengaged.
●During normal driving, do not turn off the hybrid system. Turning the hybrid sys-
tem off while driving will not cause loss of steering or braking control, but the
power assist to these systems will be lost. This will make it more difficult to steer
and brake, so you should pull over and stop the vehicle as soon as it is safe to do
so.
However, in the event of an emergency, such as if it becomes impossible to stop
the vehicle in the normal way: P. 5 3 4
●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 5 6 )
●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.
●Do not drive in excess of the speed limit. Even if the legal speed limit permits it, do
not drive over 85 mph (140 km/h) unless your vehicle has high-speed capability
tires. Driving over 85 mph (140 km/h) may result in tire failure, loss of control and
possible injury. Be sure to consult a tire dealer to determine whether the tires on
your vehicle are high-speed capability tires or not before driving at such speeds.
●The driver should pay attention to pedestrians when the vehicle is powered only
by the electric motor (traction motor). Because there is no engine sounds, the
pedestrians may misjudge the vehicle’s movement.

145
2-1. Driving procedures
2
When driving
GS_HV_U (OM30C81U)
October 13, 2015 12:41 pm
CAUTION
■When driving on slippery road surfaces
●Sudden braking, acceleration and steering may cause tire slippage and reduce
your ability to control the vehicle, resulting in an accident.
●Sudden changes in engine speed, such as engine braking caused by up-shifting
or down-shifting, may cause the vehicle to skid, resulting in an accident.
●After driving through a puddle, lightly depress the brake pedal to make sure that
the brakes are functioning properly. Wet brake pads may prevent the brakes from
functioning properly. If the brakes on only one side are wet and not functioning
properly, steering control may be affected, resulting in an accident.
■When shifting the shift lever
Be careful not to shift the shift lever with the accelerator pedal depressed.
This may lead to unexpected rapid acceleration of the vehicle that may cause an
accident and result in death or serious injury.
■When the vehicle is stopped
●Do not race the hybrid system.
If the vehicle is in any positions other than “P” or “N” the vehicle may accelerate
suddenly and unexpectedly, and may cause an accident.
●Do not leave the vehicle with the hybrid system on for a long time.
If such a situation cannot be avoided, park the vehicle in an open space and
check that exhaust fumes do not enter the vehicle interior.
●In order to prevent accidents due to the vehicle rolling away, always keep
depressing the brake pedal while the “READY” indicator is on. Apply the parking
brake as necessary.
●If the vehicle is stopped on an incline, in order to prevent accidents caused by the
vehicle rolling forward or backward, always depress the brake pedal and securely
apply the parking brake as needed.
●Avoid revving or racing the engine. Running the engine at high speed while the
vehicle is stopped may cause the exhaust system to overheat, which could result
in a fire if combustible material is nearby.

164
2-2. Instrument cluster
GS_HV_U (OM30C81U)
February 1, 2010 11:03 am
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. 5 8 1 )
■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.

5
When trouble arises
581
5-2. Steps to take in an emergency
GS_HV_U (OM30C81U)
October 13, 2015 12:41 pm
If your vehicle overheats
If your hybrid system overheats:
Stop the vehicle in a safe place and turn off the air conditioning
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.
Remove the engine compartment cover. (P. 4 6 1 )
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 immediately and call your 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

582
5-2. Steps to take in an emergency
GS_HV_U (OM30C81U)
October 13, 2015 12:41 pm
■Overheating
In the following situations, your vehicle may be overheating.
●The engine coolant temperature gauge enters the red zone or a loss of power is
experienced.
●Steam is coming from under the hood.
●The message “HYBRID SYSTEM OVERHEAT” is displayed on the multi-infor-
mation display.
CAUTION
■To prevent an accident or injury when inspecting under the hood of your vehicle
●If steam is seen coming from under the hood, do not open the hood until the
steam has subsided. The engine compartment may be very hot, causing serious
injury such as burns.
●Keep hands and clothing away from the fan and engine drive belt while the hybrid
system is operating.
●Do not loosen the radiator cap while the hybrid system and radiator are hot.
Serious injury, such as burns, may result from hot coolant and steam released
under pressure.
Add coolant if necessary.
Water can be used in an emer-
gency measure if coolant is
unavailable. (P. 5 9 3 )
Have the vehicle checked at your nearest Lexus dealer as soon as pos-
sible.
STEP6

631
Alphabetical index
GS_HV_U (OM30C81U)
February 1, 2010 11:29 am
Back-up lights
Wattage ................................................. 597
Battery
12 volt battery ...................................... 470
Checking ............................................... 470
Hybrid battery 
(Traction battery) .............................. 28
If the 12 volt battery is 
discharged ........................................ 578
Preparing and checking 
before winter .................................... 233
Bluetooth
® audio ................................... 321
Bluetooth® phone ............................... 345
Brake
Fluid .......................................................... 468
Parking brake ........................................159
Brake assist ............................................... 214
Care
Exterior ....................................................442
Interior..................................................... 445
Seat belts ............................................... 446
Cargo capacity ..................................... 228
Cargo hooks ............................................ 421
CD player/changer ............................ 282
Chains........................................................234
Child-protectors ......................................56
Child restraint system
Definition.................................................. 124
Installation................................................ 128
Installing CRS with lower 
anchors ................................................. 129
Installing CRS with seatbelts ...........131
Installing CRS with top straps .......135Child safety
Airbag precautions .............................. 114
Battery precautions ............. 472, 580
Child restraint system ........................124
Child-protectors ...................................56
How your child should wear 
the seatbelt............................................ 78
Installing child restraints................... 128
Moon roof precautions...................... 93
Power window lock switch .............. 87
Power window precautions ............89
Removed electronic key battery 
precautions....................................... 495
Seat belt comfort guide ..................... 76
Seat belt precautions .......................... 79
Seat heater precautions.................. 414
Trunk precautions................................. 62
Cigarette lighter....................................... 411
Cleaning
Exterior.................................................... 442
Interior .....................................................445
Seat belts ................................................446
Clock ........................................................ 408
Coin holder .............................................403
Compass .................................................. 429
Condenser ..............................................468
Console box ............................................ 401
Cooling system
Engine overheating............................ 581
Cruise control
Cruise control......................................... 181
Dynamic radar cruise control....... 185
Cup holders ............................................404
Curtain shield airbags.......................... 107
Customizable features ........................ 615
B
C

632
Alphabetical index
GS_HV_U (OM30C81U)
February 1, 2010 11:29 am
Daytime running light system ............172
Defogger
Rear window ........................................268
Side mirror ............................................268
Dimension ............................................... 588
Dinghy towing ........................................239
Display
Energy flow.............................................. 29
Multi-information display................ 168
Touch screen ....................................... 242
Trip information ....................................169
Warning message............................. 543
Do-it-yourself maintenance .............454
Door courtesy lights ............................395
Door pocket........................................... 405
Doors
Door lock.................................. 41, 53, 55
Rear door child protector ................ 56
Driver’s seat belt reminder light .....536
Driver’s seat position memory ........... 67
Driving
Correct posture .................................. 105
Procedures ............................................ 140
DVD player/changer..........................293
Electric power steering ....................... 214
Electronic key
If the electronic key does 
not operate properly .................... 575
Replacing battery .............................. 494Emergency, in case of
If a warning light turns on .............. 534
If a warning message is 
displayed ............................................ 543
If the electronic key does 
not operate properly ................... 575
If the hybrid system 
will not start ........................................572
If the shift lever cannot be 
shifted from “P” ................................573
If the 12 volt battery is 
discharged ....................................... 578
If you have a flat tire ........... 560, 570
If you lose your keys .........................574
If you think something is 
wrong .................................................... 531
If your vehicle becomes stuck .... 584
If your vehicle has to be stopped 
in an emergency ............................586
If your vehicle needs to be 
towed ................................................... 523
If your vehicle overheats..................581
Energy monitor ........................................ 29
Engine
ACCESSORY mode......................... 151
Compartment ..................................... 460
Hood ........................................................457
How to start the 
hybrid system.....................................150
If the hybrid system 
will not start ........................................572
Overheating ..........................................581
Power (ignition) switch ....................150D
E

635
Alphabetical index
GS_HV_U (OM30C81U)
February 1, 2010 11:29 am
Mirrors
Inside rear view mirror ...................... 83
Side mirror heater ............................. 268
Side mirrors............................................. 85
Vanity mirrors ..................................... 407
Moon roof .................................................. 90
MP3 disc ................................................. 289
Multi-information display....................168
Noise from under the vehicle .............. 18
Odometer .................................................. 161
Oil
Engine oil ............................................... 462
Opener
Fuel filler door .........................................94
Hood ....................................................... 457
Trunk........................................................... 60
Outer foot lights ................................... 395
Outside rear view mirrors
Adjusting and folding ......................... 85
Mirror position memory ....................67
Outside temperature 
display .................................................... 409
Overhead console .............................. 402
Overheating, Engine ............................581Parking brake .......................................... 159
Parking lights
Replacing light bulbs ......................... 514
Switch.......................................................... 171
Wattage ..................................................597
Personal lights ........................................ 397
Portable music player .......................... 341
Power meter .............................................. 161
Power outlet............................................. 412
Power windows ........................................ 87
Power (ignition) switch........................ 150
Pre-collision system...............................221
Radar cruise control ............................. 185
Radiator ....................................................468
Radio .......................................................... 273
Radio data system ................................ 275
Rear sunshade ........................................ 416
Rear turn signal lights
Replacing light bulbs ......................... 514
Wattage ..................................................597
Rear view monitor system.................. 210
Rear window defogger ......................268
Replacing
Electronic key battery ......................494
Fuses........................................................ 496
Light bulbs .............................................. 514
Reporting safety defects for 
U.S. owners .......................................... 624
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