Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Central Electronic Module (CEM) (2008-2012): Design: Siren
Information from the siren to the central electronic module (CEM) contains configuration and status data. This information is transmitted using serial communication.
When the alarm is armed, the siren continually sends status signals to the central electronic module (CEM).
The siren has a battery and a built-in battery charger so that it is independent of the power supply in the car. The battery charger maintains battery voltage in the built-in battery. When the alarm is armed, the power supply for the siren and the serial communication between the siren and the central electronic module (CEM) are monitored. The siren sounds if the car's power supply to the siren is cut off or if communication between the central electronic module (CEM) and the siren is interrupted. The battery and battery charger in the siren cannot be replaced separately. The entire siren must be replaced in the event of a fault.
The siren is located below the cowl. From structure week 200946 the siren is fitted in the left-hand wheel housing, above/behind the wheel. After replacing the siren, it must be configured, which is carried out using the diagnostic tool.
There are diagnostics for the siren.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.