2010 Lexus GS450h coolant temperature

161
2
When driving
GS_HV_U (OM30C81U)
February 1, 2010 11:03 am
2-2. Instrument cluster
Gauges and meters
The units used on the speedometer may differ depending on the target
region.
The following gauges, meters and display illuminate when the
“POWER” switch is in ON mode.
Power meter
Displays the instantaneous output from the hybrid system is approximate
kilowatts.
Speedometer
Displays the vehicle speed.
Fuel gauge
Displays the quantity of fuel remaining in the tank.
Engine coolant temperature gauge
Displays the engine coolant temperature.
Multi-information display
P. 1 6 8

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.

456
4-3. Do-it-yourself maintenance
GS_HV_U (OM30C81U)
October 13, 2015 12:41 pm
CAUTION
The engine compartment contains many mechanisms and fluids that may move sud-
denly, become hot, or become electrically energized. To avoid death or serious injury,
observe the following precautions.
■When working on the engine compartment
●Make sure that the indicator on the “POWER” switch and the “READY” indicator
are both off.
●Keep hands, clothing, and tools away from the moving fan and engine drive belt.
●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 flam-
mable.
■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 automatically
start to run if the air conditioning is on and/or the coolant temperature is high. 
(P. 4 6 8 )
■Safety glasses
Wear safety glasses to prevent flying or falling material, fluid spray, etc. from getting
in the eyes.
NOTICE
■If you remove the air cleaner filter
Driving with the air cleaner filter removed may cause excessive engine wear due to
dirt in the air. Also a backfire could cause a fire in the engine compartment.

5
When trouble arises
531
5-1. Essential information
GS_HV_U (OM30C81U)
January 28, 2010 10:42 am
If you think something is wrong
If you notice any of the following symptoms, your vehicle probably needs
adjustment or repair. Contact your Lexus dealer as soon as possible.
■Visible symptoms
●Fluid leaks under the vehicle
(Water dripping from the air conditioning after use is normal.)
●Flat-looking tires or uneven tire wear
●Engine coolant temperature gauge needle continually points
higher than normal
■Audible symptoms
●Changes in exhaust sound
●Excessive tire squeal when cornering
●Strange noises related to the suspension system
●Pinging or other noises related to the hybrid system
■Operational symptoms
●Engine missing, stumbling or running rough
●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

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

633
Alphabetical index
GS_HV_U (OM30C81U)
February 1, 2010 11:29 am
Engine compartment cover............... 461
Engine coolant temperature 
gauge ........................................................ 161
Engine/power control unit coolant
Capacity................................................. 593
Checking ............................................... 466
Preparing and checking 
before winter .................................... 233
Engine oil
Capacity...................................................591
Checking ............................................... 462
Preparing and checking 
before winter .................................... 233
Engine oil maintenance data ............464
Enhanced vehicle stability 
control .................................................... 214
Event data recorder............................ 532
First-aid kit storage belt....................... 421
Floor mats.................................................. 419
Fluid
Brake ....................................................... 468
Washer ....................................................474
Fog lights
Switch ........................................................ 174
Wattage ................................................. 597
Foot light .................................................. 395
Front passenger occupant 
classification system ........................... 119
Front passenger’s seat belt 
reminder light ......................................537
Front seats
Adjustment .............................................. 65
Driver’s seat position memory .......67
Front turn signal lights
Wattage ................................................. 597Fuel
Capacity ................................................ 590
Fuel gauge................................................ 161
Gas station information ..................644
Information ........................................... 598
Refueling.................................................... 94
Messages .............................................. 554
Fuel door ..................................................... 94
Fuel filler door ........................................... 94
Fuses .......................................................... 496
Garage door opener .......................... 423
Gas station information...................... 644
Gauges ........................................................ 161
Glove box ............................................... 400
Hands-free system
(for cellular phone) ..........................345
Head restraints ......................................... 72
Headlight aim ............................................511
Headlight cleaner .................................. 180
Headlights
Adaptive front lighting system....... 172
Discharge headlights 
precautions....................................... 520
Replacing light bulbs ......................... 514
Switch.......................................................... 171
Wattage ..................................................597
Heaters
Seat heaters ........................................... 413
Side mirror............................................ 268
Hill-start assist control ......................... 214
Hood .......................................................... 457
Hooks
Cargo ........................................................421
Shopping bag ........................................421
F
G
H

640
GS_HV_U (OM30C81U)
February 1, 2010 11:14 am
What to do if...
What to do if...
A tire puncturesP. 5 6 0 /
570If you have a flat tire
The hybrid system does not start
P. 9 9Immobilizer system
P. 5 7 2If the hybrid system will not start
P. 5 7 8If the 12 volt battery is discharged
The shift lever cannot be 
moved outP. 5 7 3If 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. 5 8 1If your vehicle overheats
The key is lostP. 5 74If you lose your keys
The 12 volt battery runs outP. 5 7 8If the 12 volt battery is discharged
The doors cannot be lockedP. 5 5Doors
The horn begins to soundP. 1 0 1Alarm
The vehicle is stuck in mud or
sandP. 5 8 4If the vehicle becomes stuck