Since I look at wiring diagrams 3 days a week ...figured I may as well see what do to leave the electric plunger in there...
Pretty simple found 20 schematics all with different wire colors so not sure which is what but the diagram at the bottom is what i used:
ground the black wire - same as my black wire
energize the (per schematic) BRN (brown) and LT BLU (light blue) - on mine yellow and purple**** i'll explain below
with those three wires connected the actuator retracts (no 4wd)
ground the BL/WHT (black/white) - mine was kinda grey/black but may just be old. when grounded it extends (4wd)
it would need to remain grounded to remain extended if that were how it was bult to work - but it seems GM disconnects the both the BL/WHT and the LT BLU when its fully extended, so youre not relying on constant closure of the relay to keep 4wd active, when you disconnect both wires the actuator stays extended but doesnt require power to do so