Toyota LEXUS LS430 2005 Manual page 388

If any of the following conditions occurs, this indicates a
malfunction somewhere in the components monitored by
the warning light system. Contact your Lexus dealer as
soon as possible to service the vehicle.
D The light does not come on when the ignition switch is
turned to the "ON" position, or remains on.
D The light comes on while you are driving.
A warning light turning on briefly during operation does not
indicate a problem.
CAUTION
If the "ABS" warning light remains on together with the
brake system warning light, immediately stop your
vehicle at a safe place and contact your Lexus dealer.
In this case, not only the anti−lock brake system will fail
but also the vehicle will become extremely unstable
during braking.
Drum−in−disc type parking brake system
Your vehicle has a drum−in−disc type parking brake system.
This type of brake system needs bedding−down of the brake
shoes periodically or whenever the parking brake shoes
and/or drums are replaced.
Have your Lexus dealer perform the bedding−down.
STARTING AND DRIVING
Brake assist system
If you slam the brakes on such as in an emergency or
apply the brakes more firmly than usual such as when
descending the hill with the designated number of
occupants in the vehicle, the brake assist system
provides more powerful braking.
If you slam the brakes on or apply the brakes more firmly, more
powerful braking will be applied. At this time, you may hear a
sound in the engine compartment and feel the vibrations of the
brake pedal. This does not indicate a malfunction.
The brake assist system becomes operative after the vehicle
has accelerated to a speed in excess of approximately 10 km/h
(6 mph). It stops operating when the vehicle decelerates to a
speed below approximately 5 km/h (3 mph).
For an explanation of this system's warning light, see "ABS"
warning light on page 87 or 368.
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