Lexus 2003 LS Owner's Manual page 284

STARTING AND DRIVING
NOTICE
While you are cruising with the dynamic laser cruise
control on, if the master warning light comes on, the
cruise indicator light flashes, "CHECK CRUISE
SYSTEM" appears on the multi–information display and
the warning tone sounds, turn the ignition switch off
and then on again. If the function is cancelled again
after setting or if settings cannot be made, the dynamic
laser cruise control system may be malfunctioning.
Although it is no problem to continue driving, have your
vehicle checked by your Lexus dealer.
270
Conventional (fixed speed) cruise control
mode
This mode allows you to cruise at a desired speed over
about 45 km/h (28 mph) with your foot off the accelerator
pedal.
Cruising speed can be maintained, although a slight speed
change may occur when driving up or down a gradient, within
the limits of engine performance. On steeper hills, the speed
will change more radically so it is better to drive without cruise
control.
When cruise control is on, the driving pattern of the automatic
transmission is fixed in the normal position, regardless of the
position of the selector switch.