how-to-reset-l3000-installer-code-back-to-factory-default
If you have just moved into a new house or apartment there is a good chance you have found a Honeywell LYNX Plus L3000 or ADT branded version wireless security system. Now, you are looking to change the master code, user codes or any type of zone programming but, the default 4112 installer code is not working so what do you do? No problem we are here to get you through this. 

To reset your Honeywell LYNX Plus L3000 installer code simply depress the two tabs on the top of panel > unplug backup battery > unplug power transformer > wait 10 seconds > plug battery back in > plug-in power transformer > get back to the control panel within 1 min > hold * and # until you see 20 > once you see this hit *20 > followed by 4112 > the panel will beep acknowledging you have successfully defaulted the installer code to factory.

Honeywell LYNX Plus L3000 Alarm Monitoring Options