2003 Chevrolet Impala Owner's Manual - Page 79

Disconnecting the battery for up to a year will not change the programmed mode of the programmable automatic power door locks. Trunk Lockout Protection To protect you from locking your key in the vehicle, this feature stops the power door locks from locking when the keys are in the ignition and a door is open. If a power lock switch is pressed when a door is open and the key is in the ignition, all of the doors will lock and then the driver's door will unlock. A chime will sound continuously until all doors are closed. It can be dangerous to drive with the trunk lid open because carbon monoxide (CO) gas can come into your vehicle.You can't see or smell CO. It can cause unconsciousness and even death. If you must drive with the trunk lid open or if electrical wiring or other cable connections must pass through the seal between the bodyand the trunk lid: Make sure all other windows are shut. Turn the fan on your heating or cooling system to its highest speed and select the control setting that will force outside air into your vehicle. See "Climate Controls" in the Index. If you have air outlets on or under the instrument panel, open them all the way. Leaving Your Vehicle If you are leaving the vehicle, take your keys, open your door and set the locks from inside. Then get out and close the door. See "Engine Exhaust'' in the Index.