Personal Automotive Security System: Notes

WARNING: This page is about a different car, the 1990 Cadillac Allante. However, it is still accessible from the selected car via links, so may be relevant.

The PASS Key system is designed to prevent the engine from starting if the proper resistance is not sensed from the ignition key. Of the 15 resistance values available, only one will work with each PASS Key module.

The PASS Key system prevents the engine from starting by controlling the starter enable relay and the ECM fuel enable input. If the ECM does not sense the proper pulse width modulated (PWM) signal on the fuel enable input, it will not provide fuel to the engine.

If the wrong resistance value is sensed when the ignition is turned on, the PASS Key module will not ground the starter enable circuit and will not output the fuel enable PWM signal for approximately three minutes. This prevents the engine from starting and discourages the thief from trying key codes (resistance values) at random.

If the correct resistance is sensed when the ignition is turned on, the PASS Key module will ground the starter enable circuit and output the fuel enable PWM signal. This will allow the engine to start normally.