A few things:

Alarms from the factory have a DEFAULT code built in. It is not, or should not be the code you use on a daily basis, as if so, thousands of others have it. That code is USER DEFINED, after the initial code is entered. Maintaining that user-defined code does require power. Think about why.

So, you need to determine from the manufacturer what the default code is for your make, model and assembly year - which will be from the serial number.. In theory, that should give you the default code.

Keep in mind that the manufacturer should not balk at giving this to you as it was either printed or tagged on the device when new. Kinda-Sorta like buying a safe. It comes with 12345 as the combination. Which you change (or not). But if you lose it, it is your problem. Electronics are a bit more forgiving in this sense.

Peter Wieck
Melrose Park, PA