I don't know if this was ever posted. I couldn't find any reference in a search. Toyota has directions for getting into diagnostic model in the Prius manual. Also, while looking through the manual (on CD) I discovered that there is an in-line antenna amp in the headliner just above the rear passenger door.
Search for "inspection mode". http://priuschat.com/forums/kb.php?mode=article&k=25 . If you just want the engine to idle, you don't really need this -- push the go-pedal while powered up in normal PARK, and the engine lights and revs a little. If you brake+shift to N *while* it's running, it will settle back down to idle and stay running. So for starting, revving up, and idling, the normal functionality of the car may be completely sufficient. . _H*
