Personal Automotive Security System Operation

The PASS-Key� II system prevents the engine from starting if the proper resistance is not sensed from the ignition key. Only one of the 15 resistance values available works with each PASS-Key� II decoder module.

The PASS-Key(R) II decoder module controls the starter enable relay and the Powertrain Control Module (PCM) fuel enable input. If the PASS-Key(R) II decoder module does not send the proper Pulse Width Modulated (PWM) signal to the PCM fuel enable input, the PCM does not allow fuel to be provided to the engine.

Resistor sensing contacts, located in the Ignition Key Lock Cylinder, make contact the with the key resistor pellet on the key when it is inserted. Rotating the lock applies ignition voltage to the PASS-Key(R) II decoder module, allowing the module to read the pellet resistance across terminals B7 and B8. The module compares the pellet resistance to the resistance value stored in the module.

If the key resistor pellet has the proper resistance, the PASS-Key(R) II decoder module grounds terminal A4, energizing the starter enable relay. At the same time, the module provides the cranking fuel enable signal at terminal A3 to inform the PCM to allow fuel to flow.

If the resistance is incorrect, the PASS-Key(R) II decoder module shuts down for approximately three minutes. During this interval, there is no output at terminal A3 or A4 and the "SECURITY" indicator illuminates. The module ignores the ignition switch input during this shutdown period. For this reason, the timer runs and the SECURITY" indicator remains illuminated with ignition ON or OFF.

Once the timer expires, the next time the ignition switch cycles from "OFF" to "ON," the PASS-Key(R) II decoder module timer resets. A key having the correct code can then be used to start the engine.