Circuit Operation

The PASS-Key(R) 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 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.

"SECURITY" Indicator Operation - PASS-Key(R) II
The PASS-Key(R) II system controls the "SECURITY" indicator. In normal operation, the PASS-Key(R) II decoder module controls the lamp only when the ignition is ON. There are four PASS-Key(R) II "SECURITY" indicator modes as follows.
1. Bulb Check. When the ignition is first turned on, the "SECURITY" indicator illuminates for approximately five seconds to indicate the system is operating correctly. Refer to the following bulb symptoms, if the bulb check does not operate.
2. Bulb Stays Illuminated and Engine Starts. If the "SECURITY" indicator stays illuminated after the engine starts, the PASS-Key(R) II decoder module is reading an open, short or incorrect resistance value. Verify that the PASS-Key(R) II decoder module connection at the base of the steering column is properly connected and that a good ignition key is being used.
3. Bulb Stays Illuminated and Engine Does Not Start. If the "SECURITY" indicator stays illuminated while and after attempting to start the engine and the engine does not crank or start, the PASS-Key(R) II decoder module has sensed an improper key value, has disabled the engine and set the disable timer. This specifically does not mean that the key sense circuit is open or shorted to chassis ground; refer to "Bulb Flashes and Engine Does Not Start." Remove the key from the ignition and verify that the key has the correct key code for the vehicle. The key code may be checked using J 35628-A and comparing the key code to that of other keys for the vehicle. After waiting approximately 3 minutes for the disable time to expire and the "SECURITY" indicator to go Out, attempt to start the engine with a known good key with the proper key code.
4. Bulb Flashes and Engine Does Not Start. If the "SECURITY" indicator flashes once per second and the engine does not start, the PASS-Key(R) II decoder module has sensed an open, a short or invalid (value matched none of the available 15 key codes) input from the ignition key resistor input. The PASS-Key(R) II decoder module does not start the disable timer during this operation mode. This operation mode could also be caused by malfunctioning power or ground circuits.