OPERATION

The microprocessor within the alarm siren module provides the siren unit features and functions based upon internal programming and electronic arm and disarm messages received from the intrusion module over a dedicated serial bus communication circuit. The siren module receives battery voltage on a fused B(+) circuit through a fuse in the Power Distribution Center (PDC), and receives a path to ground through a ground circuit in the headlamp and dash wire harness. These connections allow the siren to remain operational, regardless of the ignition switch position.

When the premium version of the Vehicle Theft Alarm (VTA) is armed, the siren module continuously monitors electronic message inputs from the intrusion module to sound its internal siren. While armed, the siren also enters its auto-detect mode. While in the auto-detect mode, if the siren module detects that its power supply or communication circuits are being tampered with or have been sabotaged, it will sound an audible alarm and continue to operate through an on-board backup battery. If the siren module is in its disarmed mode when its power supply or communication circuits are interrupted, the siren will not sound.

The siren module will also notify the intrusion module when the backup battery requires charging, and the intrusion module will send electronic messages that will allow the backup battery to be recharged through the battery voltage and ground circuits to the siren module only while the ignition switch is in the ON position and the engine is running. This prevents the potential discharge of the main battery while the vehicle is not being operated.

The siren will self-detect problems with its internal and external power supply and communication circuits, then send electronic messages indicating the problem to the intrusion module upon receiving an arm or disarm request message. The intrusion module will store a Diagnostic Trouble Code (DTC) for any detected alarm siren module fault. The DTC can then be retrieved with a diagnostic scan tool through the 16-way Data Link Connector (DLC) located under the driver side lower edge of the instrument panel over the Controller Area Network (CAN) data bus.

The hard wired inputs and outputs for the alarm siren module may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the alarm siren module or the electronic controls or communication between other modules and devices that provide some features of the VTA system. The most reliable, efficient, and accurate means to diagnose the alarm siren module or the electronic controls and communication related to alarm siren module operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.