Circuit Operation

PASS-Key-II is a theft deterrent system which prevents the vehicle from starting if the Ignition Key "Resistance Code" is not recognized by the Body Control Module. If the Resistance Code is not recognized, the Engine is prevented from starting in two ways: battery voltage from the Ignition Switch to the starter is disabled by a Theft Deterrent Relay and fuel to the fuel injectors is stopped without the presence of a fuel enable signal. Also, if the vehicle is equipped with the Universal Theft Deterrent System (UA6), an unrecognized "Resistance Code" will trigger an audible alarm cycle.

Resistor sensing contacts are located in the Ignition Key Lock Cylinder. These contact the Key Resistor Pellet on the key when it is inserted. When the lock is rotated, Ignition voltage is applied to the Body Control Module and pellet resistance is read at this time. The Pellet resistance is read across connector C3 terminals "C2" and "D7" which is then compared against the resistance value stored in the module. If the Key Resistance Pellet is the proper resistance, connector C3 terminal "C11" is grounded, energizing the Theft Deterrent Relay. At the same time, a signal is applied at connector C3 terminal "D8" to enable the Powertrain Control Module (PCM). When this signal is received by the PCM, it allows fuel injector pulses to begin. If the Key Resistor Pellet is the wrong value, the Body Control Module will shut down for 3 minutes + or 18 seconds. During this interval, there will be no output at connector C3 terminals "C11" or "D8" and the "SECURITY" Indicator will illuminate. The Ignition Switch input is ignored during this shut down period. For this reason, the timer will run and the "SECURITY" Indicator will remain illuminated with Ignition on or off. Once the timer has completed its 3 minute + or - 18 second shut down, the next time Ignition is cycled from off to on, the Body Control Module timer is reset. A key having the correct code can then be used to start the Engine.