2001 GMC Sierra 1500 Pickup Owner's Manual - Page 107

Automatic Transmission Operation PARK (P): This position locks your rear wheels. It's the best position to use when you start your engine because your vehicle can't move easily. If your vehicle is equipped with the AllisonR Transmission, use park for stationary operation of the Power Takeoff (PTO) (if equipped). CAUTION: It is dangerous to get out of your vehicle if the shift lever is not fully in PARK (P) with the parking brake firmly set. Your vehicle can roll. Don't leave your vehicle when the engine is running unless you have to. If you have left the engine running, the vehicle can move suddenly. You or others could be injured. To be sure your vehicle won't move, even when you're on fairly level ground, always set your parking brake and move the shift lever to PARK (P). CAUTION: (Continued) If your vehicle is equipped with an automatic transmission, it features an electronic shift position indicator within the instrument panel cluster. This display must be powered anytime the shift lever is capable of being moved out of PARK (P). This means that if your key is in OFF, rather than LOCK, there will be a small current drain on your battery which could discharge your battery over a period of time. If you have to leave your key in the ignition in OFF for an extended period, it is recommended that you remove the IGN 0 fuse from the instrument panel fuse block. See "Fuses and Circuit Breakers" in the Index. There are several different positions for your shift lever. 2-24