Anti-Theft Systems: Operation

The passlock system is designed to prevent vehicle operation if the mechanical key is not used to start the vehicle. The mechanical key, in normal operation, will turn the passlock lock cylinder. The passlock sensor (which is mounted to the passlock lock cylinder assembly) sends data by circuit 1836 to the body control module (BCM). The passlock sensor is powered by circuit 1459 from the BCM. The passlock sensor is grounded by circuit 1835 to the BCM. The BCM determines the validity of the passlock sensor data within a preset time window based on ignition switch input. The BCM will then send a coded password to the PCM by class II, circuit 1807. When the PCM receives the correct code, it will allow the fuel injectors to operate normally.

PASSLOCK MODES

• Pass Theft

  The pass theft mode is normal operation. During a normal start up, the SECURITY telltale will turn on. The telltale will turn off when:

  • the ignition is turned to the OFF or ACC position.
  • when the ignition is turned to the START position and a 3 second timer has expired.

• Short Tamper Mode (Fuel Disabled Timer Mode)

  The powertrain control module (PCM) enters the short tamper mode if the BCM detects an open voltage code (4.43v-5.00v). The BCM will send out the fuel undecided password to the PCM. The PCM will disable fuel supply to the engine for 4 seconds.

  The driver usually observes a start quickly followed by a stall when in the short tamper mode. After 4 seconds a start may again be attempted, except in one situation.

  If the PCM receives the wrong password (example: a new BCM was installed without following the relearn procedure - the SECURITY telltale will flash for 4 seconds and remain on, and the fuel injectors will remain disabled until correct relearn procedure has been completed.

• Long Tamper Mode

  The body control module (BCM) enters the long tamper mode if the BCM receives the wrong voltage code at an attempted start. The BCM will then send a disable fuel message to the PCM. The PCM will then disable the fuel injectors.

  The driver experiences the same start quickly followed by stall. The fuel will be disabled for 10 minutes and the SECURITY telltale will also flash.

• Fail Enable Mode

  In the fail enable mode, the engine is allowed to run normally because the fault occurred while the engine was running. The SECURITY telltale will remain on whenever the engine is running to alert the driver there is a problem with the passlock system and there is no passlock system protection. The engine can be restarted in the fail enable mode.

  Whenever the engine is running, the passlock system constantly monitors itself. The BCM monitors the circuits between itself and the passlock sensor. The BCM and PCM also monitor each other through the serial data link. If a problem is detected, diagnostic trouble code(s) will be set and the SECURITY telltale will be On when the engine is running.

DIAGNOSTIC TROUBLE CODES:  In either the short or long tamper mode, the BCM or the PCM will set diagnostic trouble code(s). Each module should be checked for codes (both current and history).