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Home >> BMW >> 2000 >> 323Ci 2D Convertible, Automatic >> Repair and Diagnosis (Single Page) >> Electrical >> Motors, Switches, Relays >> Central Body Electrics - Overview >> E46 Central Body Electronics >> Anti-Theft (DWA) System >> Components >> Alarm Siren

Alarm Siren

The siren from the DWA accessory kit is installed in the vehicle cowl on the passenger side of the vehicle. This location provides a secure position with loud acoustic output.

The siren contains electronic circuitry for producing the warning tone when the alarm is triggered. The siren also contains a rechargeable battery that is used to power the siren when the alarm is triggered.

Fig 1: Identifying Alarm Siren
G03395765Courtesy of BMW OF NORTH AMERICA, INC.

The rechargeable battery will allow the siren to sound if it or the vehicles battery is disconnected. The siren battery is recharged, from the vehicles battery when DWA is not in the armed state.

The siren has four wires connecting it to the system; KL 30, KL 31, Signal STDWA (arm/disarm signal from GM), and Signal SIRENE (activate siren output signal to the GM)

Fig 2: Identifying Alarm Siren Connector
G03395766Courtesy of BMW OF NORTH AMERICA, INC.

The arm/disarm output signal from the GM (STDWA) is provided to the Tilt sensor, UIS sensor and the siren simultaneously. The arm/disarm signal is a switched ground that signals the components of DWA armed/disarmed status.

The activate siren signal (SIRENE) is high whether DWA is armed or disarmed. If a monitored input activates the alarm, the high signal to the siren is switched to a 50% duty cycle at the GM. The control circuitry in the siren activates the siren driver. If the DWA is armed and the battery is disconnected the siren recognizes the normally high "SIRENE" signal as suddenly going low, the siren is also activated.

Fig 3: Circuit Diagram - Alarm Siren
G03395767Courtesy of BMW OF NORTH AMERICA, INC.