The charging system light will come on briefly when the ignition is on, 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 a generator drive belt, or another electrical problem. Have it checked right away. Driving while this light is on could drain the battery.
When this light comes on the DIC will also display the SERVICE BATTERY 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.