2003 dodge 2500, xshield 900

hello,

my name is jay and i was working today on a 2003 dodge 2500 ram 5.7l hemi,i am instaling a xshield-900s remote start alarm combo. i got everything right but not the door triggers, i know that i have to use all 4 wires and diode isolate. i found out though that you can use dome light as a door trigger. how can i do that here. when i lock the truck with the remote it locks and all fine but little after maybe like 15 or 20 second the alarm goes off crasy.if this doesnt happen , any button i push on the remote will set the alarm. there is so many tan door trigger wires under the foot emergency brake, and i thought i can use the dome light instead as a trigger because it works with all doors.the brown dome light wire is ground when i open any door, but after the dome light delay is gone and light off, it becomes 12 volt. any help is appreciated

thanks, jay