Century V6-3100 3.1L VIN M SFI (1998)
Body Control Module: Description and Operation
Pass-Key II Theft Deterrent
The Personal Automotive Security System (PASS-Key II) is a vehicle theft deterrent system. The PASS-Key II is designed to prevent vehicle theft by
disabling the engine from starting unless an ignition key with a specific resistor pellet code is used in the ignition lock cylinder.
The ignition lock cylinder contains the resistor sensing contacts. These contacts touch the resistor pellet embedded in the ignition key. When the ignition
key is inserted in the ignition lock cylinder, the resistor pellet completes the key detection circuit (circuits 1073 and 1074).
When the ignition switch is turned from the OFF to the RUN position, the Body Control Module (BCM) applies a 5V reference voltage to circuit 1073.
Then, the BCM reads the resistor pellet code and compares the stored resistor pellet code against the ignition key resistor pellet code for a correct match.
Upon detecting a correct match, the BCM sends a fuel enable password to the Powertrain Control Module (PCM) through the Class II serial data link.
As a result, the PCM enables the theft deterrent relay, and allows fuel delivery to the engine.
If the key resistor pellet is incorrect, the PCM disables the theft deterrent relay, and stops fuel delivery to the engine. This vehicle disable period state
will last approximately 3 minutes during which time the SECURITY indicator will flash when the ignition switch in the RUN position. Disconnecting
the battery will not clear the timer sequence, it will resume when battery power is restored. Even if a proper key is inserted during the vehicle disable
period, the vehicle will not start until the 3 minute time period has elapsed. After this 3 minute time period, the SECURITY indicator will change from
a flashing state to a solid on state. At this time, the BCM enters the theft deterrent re-learn mode. Also, the engine will start if the correct ignition key
resistor pellet is used.
Refer to PASS-Key(R) II for more information. See: Accessories and Optional Equipment/Antitheft and Alarm Systems
