96 tahoe positive door trigger?

i have a code alarm pc7600 gen2 in my 96 tahoe.. when i get out of the car and set the alarm it sets completely and the dome light stays on...

i have the same unit in my 93 Ford SHO and when the dome is still active the alarm only prearms, then when the dome shuts it arms completely....

i am thinking maybe this is due to the fact that the SHO has a positive door trigger that somehow works off the dome? 

whereas in the tahoe i am using a negative?

can anyone tell me if there is a wire within the 96 tahoe that i can use for a positive trigger for when the doors open that works in conjunction with the dome? right now i am using the purple neg at the drivers door pin...

Thanks in advance to any and all who can help.....

If the alarm has a positive door trigger hook that to the floor light so when any door opens the light comes on and triggers the + door trigger input, this sounds like how the SHO is hooked up to me.

auex,

     it's not really a problem.....

96 tahoe.. Code alarm PC7600 Gen2..

when i exit the vehicle and i set the alarm it arms completely whether the dome light is on or not... it should detect the dome and pre arm, then Arm once dome goes out... as does my 93 sho

i believe the dome is tapped into the white wire off the switch and the door trigger is tapped into the purple - at the drivers door pin....

the sho has a positive system and it works fine...... trying the old process of elimination to diagnose