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 A7 is applied to the PASS-Key Decoder Module terminal A2. This signals the decoder module to compare the resistor pellet value to the value stored in the decoder module's memory. If the pellet is the proper resistance, the module's starter enable terminal A4 is grounded, energizing the Starter Enable Relay. 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.

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 resistor pellet value for any reason, the decoder module will disable starting, but will not start the shutdown cycle.

Theft System Armed Indicator
If the decoder module senses ignition voltage at terminal A2, the decoder module's indicator control terminal A5 will ground the THEFT SYSTEM ARMED 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 THEFT SYSTEM ARMED Indicator.

Warning Messages
Two main messages are displayed on the Information Center concerning the system's operation. The PCM commands the Climate Control/Driver Information Center (CCDIC) 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. 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
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) de-energizing the Starter Enable Relay. 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.