Dear Tom & Ray,

General Motors has a anti - theft system called:

" Passlock "

It uses a signal from the ignition switch,

fed into a electronic box under the dash board,

which stops gas flow , if the signal is absent.

I’ve found a method of defeating this system, should it be defective , because of a bad ignition switch.

It requires cutting the ignition switch wire,

while the engine is running, causing the system to fail enabled. And, that condition will remain enabled , as long as the battery is connected.

I’d like to duplicate that signal , comming from the ignition switch , so I can replace the battery when necessary.

What is that signal?