Alarm keeps going off

The car-2008 Prius Touring PKG #6 177k miles, clean Carfax, clean title, no accidents, flood or salvage history.

There are no aftermarket accessories or alarm system installed. Just the dealer/port installed illumination kit with under dash lights, cup holder LEDs and center console light.

Problem:

Whenever the car is locked after about 1-2 minutes the alarm (horn and lights) starts going off. A few times while driving the triangle and door open lights would come on briefly and go out ( I have not been able to duplicate this in the last two weeks. If I sit in the car with the doors closed, the car off and the dome light set to come on when door opened the dome light will come on whenever there is an electrical draw such as putting my foot on the brake or the random ABS pump running.

What I have tried and determined so far:

I have individually and altogether replaced the 4 door plungers with plungers from another car w/o problem. I have also disconnected them one at a time and all together. When they are disconnected the car thinks the door is closed ( the door open light goes out).

I have installed a brand new Toyota 12V battery that I charged prior and tested.

I believe the disruption in power is causing the door open light/dome light to come on which sets off the alarm. just not sure why. I have tried sitting in other cars to see if this happens also. It doesn't.

Is there a body control module somewhere that I could swap out? I have two parts cars.

There are some History codes
B1200 Body ECU Communications Stop
B1207 SmartKey ECU Communications Stop
B1271 Combination Meter ECU Communications Stop

 

Actually.... There WAS an aftermarket alarm system behind the dash that had been disable but once removed the problem went away.