2003 GMC Yukon Owner's Manual - Page 196

If, after several seconds, all status indicator lights remain on, or if there are no lights at all, there may be a problem with the lights or the passenger sensing system. See your dealer for service. Battery Warning Light If this light is displayed when the engine is running, you may have a problem with your charging system. {CAUTION: If the off indicator and the air bag readiness light ever come on together, it means that something may be wrong with the air bag system. If this ever happens, have the vehicle serviced promptly, because an adult-size person sitting in the right front passenger seat may not have the protection of the frontal air bag. See "Air Bag Readiness Light" in the Index. The battery display will also stay on while the key is in RUN until the engine is started. If the light stays on after starting the engine it could indicate a problem with the generator drive belt, or some other charging system problem. Have it checked right away. Driving with this light displayed could drain your battery. If you must drive a short distance with this light displayed, it helps to turn off all your accessories, such as the radio and the air conditioner. 3-42