On mine (Power Gear), in order to turn it on:
IGN must be ON, start the engine, as the pump draws a LOT of current.
Park brake SET
Transmission in P or N
1999 Fleetwood Southwind 35S (Ford F53 6.8L V10 275hp 4R100 4 spd trans) - Toad 2003 Saturn Vue.
It won't do MACH 2, but I can get a sandwich and take a pee.