The charging system light will come on briefly when you turn on the ignition, but the engine is not running, as a check to show you it is working.
It should go out once the engine is running. If it stays on, or comes on while you are driving, you may have a problem with the charging system. It could indicate that you have problems with the generator, the generator drive belt, or another electrical problem. Have it checked right away. Driving while this light is on could drain your battery.
When this light comes on, the Driver Information Center (DIC) will also display the SERVICE BATTERY NOT CHARGING SYSTEM message. See DIC Warnings and Messages for more information.
If you must drive a short distance with the light on, be certain to turn off all your accessories, such as the radio and air conditioner, to reduce the drain on your battery.