2008 LEXUS RX400H Check system light

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4-3. Do-it-yourself maintenance
4
Maintenance and care
RX400h_U
■If you push the tire pressure warning reset switch accidentally
If initialization is performed, adjust the tire inflation pressure to the specified level
and initialize the tire pressure warning system again.
■When the initialization of the tire pressure warning system has failed
Initialization can be completed in a few minutes. However, in the following cases,
the settings have not been recorded and the system will not operate properly. If
repeated attempts to record tire inflation pressure settings are unsuccessful, have
the vehicle inspected by your Lexus dealer.
●When operating the tire pressure warning reset switch, the tire pressure warning
light does not flash 3 times.
●After carrying out the initialization procedure, the tire pressure warning light
blinks for 1 minute then stays on after driving for about 20 minutes.
■Routine tire inflation pressure checks
The tire pressure warning system does not replace routine tire inflation pressure
checks. Make sure to check tire inflation pressure as part of your routine of daily
vehicle checks.
■Tire pressure warning system certificationFor vehicles sold in the U.S.A.
This device complies with Part 15 of the FCC Rules. Operation is subject to the fol-
lowing two conditions: (1) this device may not cause harmful interference, and (2)
this device must accept any interference received, including interference that may
cause undesired operation.
NOTICE:
This equipment has been tested and found to comply with the limits for a Class B
digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to
provide reasonable protection against harmful interference in a residential installa-
tion. This equipment generates, uses and can radiate radio frequency energy and, if
not installed and used in accordance with the instructions, may cause harmful inter-
ference to radio communications. However, there is no guarantee that interference
will not occur in a particular installation. If this equipment does cause harmful inter-
ference to radio or television reception, which can be determined by turning the
equipment off and on, the user is encouraged to try to correct the interference by
one or more of the following measures:
●Reorient or relocate the receiving antenna.
●Increase the separation between the equipment and receiver.

5
When trouble arises
393
5-2. Steps to take in an emergency
RX400h_U
■Key reminder buzzer
The buzzer indicates that the key has not been removed from the engine switch
(with the engine switch in the ACC or LOCK position and the driver’s door
opened).
■If the malfunction indicator lamp comes on while driving
First check the following:
●Is your vehicle low on gas?
If it is, refuel the vehicle immediately.
●Is the fuel tank cap loose?
If it is, tighten it securely.
The lamp will go off after taking several driving trips.
If the light does not go off even after several trips, contact your Lexus dealer as soon
as possible.
■Front passenger detection sensor and passenger seat belt reminder
●If luggage is placed on the front passenger seat, the front passenger detection
sensor may cause the warning light to flash, even if a passenger is not sitting in the
seat.
●If a cushion is placed on the seat, the sensor may not detect a passenger, and the
warning light may not operate properly.
■Changing the engine oil (U.S.A. only)
Make sure to reset the oil change system. ( →P. 3 2 1 )
■When the tire pressure warning light comes on
Check the tire inflation pressure and adjust to the appropriate level. Pushing the tire
pressure warning reset switch does not turn off the tire pressure warning light.
■The tire pressure warning light may turn on due to natural causes
The tire pressure warning light may turn on due to natural causes such as natural air
leaks or tire inflation pressure changes caused by temperature. In this case, adjust-
ing the tire inflation pressure will turn off the warning light (after a few minutes).

394
5-2. Steps to take in an emergency
RX400h_U
■When a tires is replaced with a spare tire
The spare tire is also equipped with the tire pressure warning valve and transmitter.
The tire pressure warning light will turn on if the tire inflation pressure of the spare
tire is low. If a tire goes flat, even though the flat tire is replaced with the spare tire,
the tire pressure warning light does not turn off. Replace the spare tire with the
repaired tire and adjust the proper tire inflation pressure. The tire pressure warning
light will turn off after a few minutes.
■If the tire pressure warning system is inoperative
The tire pressure warning system will be disabled in the following conditions:
(When the condition becomes normal, the system will work properly.)
●If tires not equipped with tire pressure warning valves and transmitters are used.
●If the ID code on the tire pressure warning valves and transmitters is not regis-
tered in the tire pressure warning computer.
●If the tire pressure warning select switch is set to a different tire setting.
●If the tire inflation pressure is 73 psi (500 kPa, 5.1 kgf/cm2 or bar) or higher.
The tire pressure warning system may be disabled in the following conditions:
(When the condition becomes normal, the system will work properly.)
●If electronic devices or facilities using similar radio wave frequencies are nearby.
●If a radio set at similar frequencies is in use in the vehicle.
●If a window tint that affects the radio wave signals is installed.
●If there is a lot of snow or ice on the vehicle, in particular around the wheels or
wheel housings.
●If non-genuine Lexus wheels are used. (Even if you use Lexus wheels, the tire
pressure warning system may not work properly with some types of tires.)
●If tire chains are used.
●If the spare tire is in a location subject to poor radio wave signal reception.
●If a large metallic object which can interfere with signal reception is put in the
trunk.
■If the tire pressure warning light comes on after blinking for 1 minute frequently
If the tire pressure warning light comes on after blinking for 1 minute frequently
when the engine switch is turned to ON position, have it checked by your Lexus
dealer.

5
When trouble arises
395
5-2. Steps to take in an emergency
RX400h_U
CAUTION
■If the tire pressure warning light comes on
Be sure to observe the following precautions. Failure to do so could cause loss of
vehicle control and result in death or serious injury.
●Stop your vehicle in a safe place as soon as possible. Adjust the tire inflation pres-
sure immediately.
●If the tire pressure warning light comes on even after tire inflation pressure adjust-
ment, it is probable that you have a flat tire. Check the tires. If the tire is flat,
change to the spare tire and have the flat tire repaired by the nearest Lexus
dealer.
●Avoid abrupt maneuvering and braking. If the vehicle tires deteriorate, you could
lose control of the steering wheel or the brakes.
■If a blowout or sudden air leakage should occur
The tire pressure warning system may not activate immediately.

396
5-2. Steps to take in an emergency
RX400h_U
CAUTION
■Maintenance of the tires
Each tire, including the spare (if provided), should be checked monthly when cold
and inflated to the inflation pressure recommended by the vehicle manufacturer on
the vehicle placard or tire inflation pressure label (tire and load information label).
(If your vehicle has tires of a different size than the size indicated on the vehicle
placard or tire inflation pressure label [tire and load information label], you should
determine the proper tire inflation pressure for those tires.)
As an added safety feature, your vehicle has been equipped with a tire pressure
monitoring system (TPMS-tire pressure warning system) that illuminates a low tire
pressure telltale (tire pressure warning light) when one or more of your tires is sig-
nificantly under-inflated. Accordingly, when the low tire pressure telltale (tire pres-
sure warning light) illuminates, you should stop and check your tires as soon as
possible, and inflate them to the proper pressure. Driving on a significantly under-
inflated tire causes the tire to overheat and can lead to tire failure. Under-inflation
also reduces fuel efficiency and tire tread life, and may affect the vehicle's handling
and stopping ability.
Please note that the TPMS (tire pressure warning system) is not a substitute for
proper tire maintenance, and it is the driver's responsibility to maintain correct tire
pressure, even if under-inflation has not reached the level to trigger illumination of
the TPMS low tire pressure telltale (tire pressure warning light).
Your vehicle has also been equipped with a TPMS (tire pressure warning system)
malfunction indicator to indicate when the system is not operating properly. The
TPMS (tire pressure warning system) malfunction indicator is combined with the
low tire pressure telltale (tire pressure warning light). When the system detects a
malfunction, the telltale will flash for approximately one minute and then remain
continuously illuminated. This sequence will continue upon subsequent vehicle
start-ups as long as the malfunction exists. When the malfunction indicator is illumi-
nated, the system may not be able to detect or signal low tire pressure as intended.
TPMS (tire pressure warning system) malfunctions may occur for a variety of rea-
sons, including the installation of replacement or alternate tires or wheels on the
vehicle that prevent the TPMS (tire pressure warning system) from functioning
properly. Always check the TPMS (tire pressure warning system) malfunction tell-
tale after replacing one or more tires or wheels on your vehicle to ensure that the
replacement or alternate tires and wheels allow the TPMS (tire pressure warning
system) to continue to function properly.

5
When trouble arises
407
5-2. Steps to take in an emergency
RX400h_U
Have the malfunction repaired immediately.After taking the specified steps to co rrect the suspected problem, check
that the warning light turns off.
■Changing the engine oil (U.S.A. only)
Make sure to reset the oil change system. ( →P. 3 2 1 )
■Warning light display in radar cruise mode
In the following cases, the warning light may not be displayed even if vehicle-to-
vehicle distance closes.
●When your vehicle and the vehicle ahead are traveling at the same speed or the
vehicle ahead is traveling more quickly than your vehicle
●When the vehicle ahead is traveling at a very low speed
●Immediately after cruise control speed is set
●At the instant the accelerator pedal is depressed
Wa r n i n g m e s s a g eDetailsCorrection
procedure
(Comes on for 8 seconds.)
Indicates that the fuel
door left open after refuel-
ing when start the vehicle/
leave the fuel door open
for more than 30 minutes
during refueling.
Close the fuel lid.

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5-2. Steps to take in an emergency
RX400h_U
■Starting the hybrid system when the 12-volt battery is discharged
The hybrid system cannot be started by push-starting.
■Avoiding a discharged battery
●Turn off the headlights and the audio system while the hybrid system is turned off.
●Turn off any unnecessary electrical components when the vehicle is running at a
low speed for an extended period, such as in heavy traffic, etc.
■After recharging the 12-volt battery
(→ P. 3 2 8 )
■When the battery is removed or discharged
The power windows, power back door and moon roof must be initialized.
(→ P. 4 6 2 )
CAUTION
■Avoiding battery fires or explosions
Observe the following precautions to prevent accidentally igniting the flammable
gas that may be emitted from the battery.
●Make sure the jumper cable is connected to the correct terminal and that it is not
unintentionally in contact with any part other than the intended terminal.
●Do not allow the jumper cables to come into contact with the “+” and “-” termi-
nals.
●Do not allow open flame or use matches, cigarette lighters or smoke near the
battery.
Once the vehicle’s hybrid system has started, remove the
jumper cables in the exact reverse order in which they were
connected.
Once the hybrid system starts, have the vehicle checked at your Lexus
dealer as soon as possible.STEP5

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6-1. Specifications
RX400h_U
Electrical system
12-volt battery
Open voltage at
68°F (20 °C):12.6  12.8 V Fully charged
12.2 
12.4 V Half charged
11.8 
12.0 V Discharged
(Voltage checked 20 minutes after the
key is removed from the engine switch
with all the lights turned off)
Charging rates5 A max.