P1572 Immobilizer (not antenna)

[turbomacncheese]

Car was running just fine (well, fine enough to be jumped off the road anyway). Sat for a while, then wouldn't start. Battery failed shortly after. New battery, cranks, no start. P1572 is the only real clue I have. Supporting details: security light on the combo doesn't light up at all ever (I'm certain it did before) and the green ring light around the ignition doesn't light up at all ever (I'm not quite certain that it did before).

I'm stuck on troubleshooting this mess besides cleaning some small amounts of corrosion off the plugs/pins for the immobilizer unit and body integrated unit.

Any ideas?

Edit: Just found this, I guess it's as good a place to start as any -
sec light.png