Parasitic battery drain....double beep???

[Box7774]

Question for you guys....new to me 2001 box base....Previous owner installed an aftermarket radio. My car double beeps when locked. I read several posts about this issue to get a feel for the culprit. I ran out to my garage and checked the console but it was shut all the way. Anyway as I understand it, my oem stereo was monitored by the alarm system so by the previous owner removing it I guess this could be my double beep issue. People install after market radios all the time in our cars how do they get around this alarm issue?

My other question is this. My battery is relatively new and yet it is losing volts and currently reading 12.4. I am wondering if this open circuit in the alarm could be causing battery drain????? I will be purchasing a new battery tomorrow and monitoring its voltage every few days. If the new batt is getting drained as well I will know for sure that I have an issue.

Last question....
I own a obd cheapo from Harbor Freight. Will I be able to use this on my 01 Boxster to see codes? Probably a dumb question but ....a question none the less