Mercedes B Klasse Electric Siren Communication Fault

I encountered a comparable vehicle security problem with my previous Audi A4. The issue was intermittent, and I initially suspected the siren itself. However, after a thorough wiring inspection, a corroded connector in the rear near the alarm module was identified. Have you inspected the wiring harness and connectors associated with the siren, paying particular attention to any signs of corrosion or physical damage? Also, is the vehicle throwing any other related error codes?

Thanks for the information. The error memory only shows the siren communication fault. Where specifically was the alarm module located in your A4? I will focus my attention on the wiring around that area, to see if there is a similar configuration. Do you know where to locate wiring diagrams?

In my A4, the alarm module was situated in the right rear quarter panel, behind the trim. Accessing it required partial disassembly of the trunk lining. Unfortunately, I do not have access to wiring diagrams, and I would strongly advise consulting a qualified automotive electrician or the Mercedes-Benz workshop for accurate documentation and proper diagnostic procedures. They will possess the necessary expertise and equipment to safely and effectively address your alarm system fault.

Thank you for the advice; it's much appreciated. I followed your suggestion and took it to the workshop. The wiring to the siren had indeed corroded at a connector, as you suspected. Replacing the section of damaged wiring resolved the communication fault and restored the alarm system to full functionality.