How do you bypass the passive anti-theft system on a 1999 f-150?

Answer 1

To disconnect it completely cannot be done because it is connected to the main engine computer of the vehicle, but there are ways to bypass the system. It all depends on what you really want to accomplish by the bypass.

The easiest way is to buy a bypass module and have it installed at your local automotive alarm / electronics installation center. This can be connected to an aftermarket alarm so that when you disarm the aftermarket alarm the bypass module disables the anti=theft unit. These bypass units will trick the anti-theft module to believing that there is a validly coded key in the ignition and therefore will allow the vehicle to start without a previously programed key.

Another way is to use a spare key that has been programed to the vehicle and wrapping it around the head of the key with 22 gauge insulated telephone wire, about 15 turns is enough, and attaching the ends in series with the antenna wire of the anti-theft system that is located at the ignition switch. This will have the same effect as the bypass module in the previous paragraph.