[davepl]

This is TOTALLY from memory from having looked at the instruction sheet a couple of years ago on a friend's truck, so please double-check it. But I'm a visual learner so this should be close:

On the bottom right of the Vintage wiring diagram, you'll find a manual override knob which activates a blue or white wire. That's the one you want to tie your ECM's green wire to. When the green wire goes LOW (ground signal), it will act like the manual override switch and activate the relay just like the switch would if you manually flipped it.