the orange light should not be coming on when only on key position 1, although the pump should run. i would first start by swapping out the ecu and see what happens. there are 3 different abs modules for cossies, yellow (3 door and early 2wd sapph), red (2wd sapph) and green (4x4). the colour refers to the multiplug and socket colour, and you need to swap it for one of the same colour, otherwise the multiplug will not fit as they are wired differently.

let us know how you get on.