2007 GMC Acadia Owner's Manual - Page 124

Ignition Positions With the key in the ignition, you can turn it to four different positions. B (ACCESSORY): This position allows you to use things like the radio and the windshield wipers while the engine is off. This position will also allow you to turn off the engine. Use ACCESSORY if you must have your vehicle in motion while the engine is off, for example, if your vehicle is being pushed or towed. C (ON): This is the position that the switch returns to after you start your engine and release the key. The switch stays in ON when the engine is running. But even when the engine is not running, you can use ON to operate your electrical power accessories, and to display some instrument panel warning lights. The battery could be drained if you leave the key in the ACCESSORY or ON position with the engine off. You may not be able to start your vehicle if the battery is allowed to drain for an extended period of time. D (START): This position starts the engine. When the engine starts, release the key. The ignition switch will return to ON for normal driving. A (OFF): This is the only position in which you can remove the key. This position locks the ignition and transmission. Notice: Using a tool to force the key from the ignition switch could cause damage or break the key. Use the correct key and turn the key only with your hand. Make sure the key is all the way in. If none of this works, then your vehicle needs service. 124