Toyota Lexusc Owner's Handbook Manual page 110

(e) Discharge Warning Light
This light warns that the battery is being discharged.
If it comes on while you are driving, stop the vehicle, turn off the
engine, and check for the cause. Look first at the engine drive
belt.
D If it is loose or broken, the generator will not charge the
battery properly.
NOTICE
Do not continue driving if the engine drive belt is broken
or loose.
GAUGES, METERS AND SERVICE REMINDER INDICATORS
D If the belt is O.K., there is a problem somewhere in the
charging system.
The engine ignition will continue to operate, however, until the
battery is discharged. Turn off the air conditioning, blower,
radio, etc., and drive directly to the nearest Lexus dealer or
repair shop.
91