Pass-Key

CIRCUIT OPERATION

PASS-Key prevents vehicle starting by disabling the fuel injection system and starter circuit.

When a key is inserted in the ignition, resistor sensing contacts located in the cylinder contact the resistor pellet in the key. When the lock is rotated to the RUN position, battery voltage from Fuse A9 is applied to the PASS-Key(R) Decoder Module terminal A2. This signals the decoder module to compare the resistor pellet value to the value stored in the decoder modules memory. If the pellet is the proper resistance, the module's starter enable terminal A4 is grounded, providing a ground for the [1][2]Starter Enable Relay coil. At the same time, the module's cranking fuel enable terminal A3 applies a signal to the Powertrain Control Module (PCM). When this signal is received by the PCM, it enables the fuel injectors.

Power and Ground
Battery voltage is applied at all times to the PASS Key(R) Decoder Module at terminal A1 (to power the module) through Fuse B3 and CKT 1040. The decoder module is grounded at ground G400 through CKT 803 at terminal B5.

Battery voltage is applied to decoder module terminal A2 when the ignition is in RUN, BULB TEST or START through Fuse A9 and CKT 1276. The ignition input is primarily used as a wake-up to the system but will power the system if the BAT input circuit opens.

System Shutdown
If the key resistor pellet is the wrong value, the decoder module will shut down for approximately three minutes. During this shutdown interval there is no output at the decoder module's terminals A3 or A4.

If the ignition is turned to RUN again during the shut down interval even with the correct key, the decoder module will ignore the input at terminal A2 until the shutdown cycle is completed.

Once the decoder module has completed its shutdown cycle, a key having the correct code can be used to start the engine when the ignition is turned from OFF to RUN.

If the decoder module is unable to read the key resist0r pellet value for any reason, the decoder module will disable starting, but will not start the shutdown cycle.

SECURITY Indicator
When the decoder module senses ignition voltage at terminal A2, the decoder module's indicator control terminal A5 will ground the SECURITY Indicator for approximately five seconds as a bulb check function. Should the key resistance not match the programmed value in the module, the indicator will remain on and the engine will not crank. The indicator will flash if the decoder module is unable to read the key resistor pellet value and the engine will not crank. If the decoder module is unprogrammed and unable to read the key pellet resistor value, the indicator will flash but the engine will start.

After a correct key code has been read, if during that ignition cycle an open or short is detected in the resistor sensing circuit for more than 1 minute the indicator will remain on as long as the fault condition exists. When the ignition is cycled off and back to run again the engine will restart. It should be noted that the Theft Deterrent Module also controls the SECURITY Indicator.

Warning Messages
Two main messages are displayed on the Driver Information Center (DIC) concerning the system's operation. The PCM commands the Instrument Panel Cluster (IPC) to turn on these messages through the UART data line.

"STARTING DISABLED DUE TO THEFT SYSTEM REMOVE IGNITION KEY" will be displayed whenever the ignition is turned from OFF to RUN and the PCM does not receive the cranking fuel enable input from the decoder module. This can be caused by one of the following conditions:

^ Incorrect key code is read
^ Cranking fuel enable circuit failed when the ignition was off
^ Loss of power or ground to the decoder module

After this message is displayed several messages indicating the time remaining will be displayed.

Another message that may be displayed is "THEFT SYSTEM PROBLEM CAR MAY NOT RESTART." This message will appear when the engine is running and a malfunction occurs in the fuel enable circuit or the decoder module loses its power or ground. The car will continue to run when this message appears but if the malfunction is due to a loss of power or ground, the car will not restart. The PCM will set code 58 when this message appears.

Starter Inhibit (Northstar only)
After the PCM confirms that the engine is running, the PCM closes the starter inhibit output (terminal 3E6) grounding the decoder module's starter inhibit input (terminal A7). This causes the decoder module to open the starter enable output (terminal A4) removing ground from the [1][2]Starter Enable Relay coil. The Starter Solenoid can no longer be energized when the Ignition Switch is turned to START. The PCM will open the starter inhibit output when the engine stops running, allowing the decoder module to close the starter enable output.