2005 Subaru Legacy Owner's Manual - Page 147

Keys and doors NOTE If the code entered the second time is not identical to the code entered the first time, an error will occur. In this event, perform the procedure again beginning with part 5. If an error occurs five times, perform the procedure again starting with part 3. 10.If you wish to program another transmitter code into the system (up to four transmitter codes can be programmed into the system), perform the procedure beginning with part 4. When you have finished programming all of the necessary transmitter codes into the system, remove the key from the ignition switch. 11.Test every registered transmitter to confirm correct operation. ! Deleting old transmitter codes The control unit of the keyless entry system has four memory locations to store transmitter codes, giving it the ability to operate with up to four transmitters. When you lose a transmitter, the lost transmitter's code remains in the memory. For security reasons, lost transmitter codes should be deleted from the memory. To delete old transmitter codes, program four transmitter codes into the system. If you have only one current transmitter, program it four times. If you have two current transmitters, program each one twice. If you have three current transmitters, program two of them 2-22 once and the third one twice. This process will leave only current transmitter codes in the system's memory. NOTE Make sure no one else is operating their keyless entry system within range of your vehicle when programming transmitters. If someone else were to operate their remote transmitter while you are programming your transmitters, it is possible that their transmitter code will be programmed into your system, allowing them unauthorized access to your vehicle.