prestige 786 bypass wire?

What wire do you use to power upm a dei 555g bypass?  I have the bypass grounded out  and it works but I cant figure out which wire off of the alarm will power it up. There are four wires which are supposed to provide ground at different times but none of them will activate the bypass. I ran a relay off of one of the ignition wires to power up the bypass and it starts but the security light comes on until you put the key in.

Light blue, Ignition 3, in the big plug with all the parking/brake/door trigger wires. The light blue wire makes a ground whenever the remote starter is on.

Thanks I appreciate it. Any idea which where to locate the horn wire? It is on a 2002 rendezvous

steering column or bcm

I believe it is in the airbag harness on that vehicle.