Lexus GS430 User Manual page 441

(h) Vehicle−to−vehicle distance control mode failure
warning
G31020
If there is trouble somewhere in the dynamic radar cruise
control while the vehicle−to−vehicle distance control mode is
on, the "CRUISE" indicator light in the instrument cluster
flashes, the master warning light comes on and the warning
tone sounds, and one or more of the following warning
messages will appear on the multi−information display.
D "CLEAN RADAR SENSOR"
D "CRUISE NOT AVAILABLE"
D "CHECK CRUISE SYSTEM"
If any warning message shown above appears, the preset
speed automatically cancels out.
STARTING AND DRIVING
G13073
If the system cannot
vehicle−to−vehicle distance because of a dirty millimeter
wave radar sensor or grille cover while the dynamic radar
cruise control is on, the above message appears.
If this message appears, clean the sensor and grille cover with
a soft cloth and try setting the preset speed again. If the dirt
is removed without cleaning, the system will automatically
enter the "RADAR READY" mode. If the system does not enter
the "RADAR READY" mode even after cleaning or the
message remains on the display, the system might be
malfunctioning. Although it is no problem to continue driving,
contact your Lexus dealer.
easily measure the
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