This often tells you that your battery is low. See if you can purchase a new battery, then replace your old battery with a new battery. This problem should be resolved once you do this.

Every one of the non-mechanics above answered your answer incorrectly! When the battery light illuminates on your dash it means your alternator is not charging betwen 13.5 - 14.2 volts.

If the battery tests good, get a wiring diagram and check out the ELD module. The electronic load detection module tells the alternator the current state of the electrical. If you've added high power stereo gear and connected it directly to the battery, that can really screw up the ELD.

If battery is fairly new, bring it back to the store and have it checked since its still under warranty.

It could also be that your alternator is going bad and is not fully charging the battery, so when the battery power gets low, the battery light comes on.