FLASHING MARKER LIGHTS!!!!

[f5fstop]

Now, let me get this correct. You tapped into the hot wire (Dark Blue) that is fed by the BCM (body control module) to the front flashers?
You then connected this voltage source to the ground side of the side marker lamp that has B+ to the other side of the bulb; through the filament, when the park lamps are on?
So, now with the park lamps on, you have power flowing through the bulb from the PRK/LP relay, and then into the circuit that powers the turn signal bulb. This power will naturally flow to the BCM, which at this state is an open switch, waiting for the turn signal lever signal to close the circuit and flash the lamps.
OK; your BCM, your Hummer. Just remember, if sometime in the future your BCM fries, and the tech does what he is supposed to do and that is troubleshoot the circuits, and a good tech will test for both opens and shorts to power, and when he checks for power at BCM connector C1, terminals B1 or B2, he will find 12 volts (minus whatever the drop is across the bulb filament).
He will then track down this short to power, and that might take hours, find the non-factory splice, and the dealer will call and say that the cause was due to improper wiring and that you are responsible for the diagnosis and the BCM replacement. GM will not cover this either, and to be honest, they shouldn't.
Installation should have had low resistance relays in each turn signal circuit to protect the BCM.
Hopefully, these circuits of the BCM have diodes to protect the circuit internal to the BCM.