may spike sensor din ang mga alarm. spike meaning changes in load sa electricals. thus when you open the trunk or back door which is not directly connected to the door sensors it also triggers the alarm. try to pull out the positive terminal of your HU while the alarm is armed, mag aalarm yan. what you can do is connect the sensor of your trunk/tailgate to any of the four doors para kasma siya siya sa arming. I did this to my Patrol. My mannix alarm arms in 30 second after you turn the engine off open the door and closed it.