Many Garmin GPS devices come with an antitheft feature that enables you to lock your Garmin device. To lock your Garmin GPS unit, you set a four-digit PIN (personal identification number) and a security location. Every time you turn your Garmin GPS on, you must enter your PIN or drive to your security location to unlock and use the Garmin GPS. To reset your Garmin PIN, you must first unlock your Garmin GPS device.
Power your Garmin GPS device on and enter your four-digit PIN. If you have forgotten your PIN, make sure your GPS antenna is up and able to acquire satellite signal and drive to your security location to unlock your Garmin device.
Touch "Settings" (the wrench tool icon) on your menu and select "System."
Click "Restore" at the bottom of the GPS System Settings screen and hit "OK."
Touch the button next to "Garmin Lock" and touch "OK."
Enter a new four-digit PIN twice and hit "Yes" to accept the PIN. Your Garmin GPS device tells you to set a security location in case you forget your PIN.
Hit "OK" and drive to your security location. Touch "Set."
If you forgot your PIN and security location (or just can't get to your security location for any reason), you need to send your GPS device to Garmin--along with a proof of ownership--to unlock it.