Mercedes M Klasse Diesel Alarm Problem

That quoted price isn't too bad. Before you tear into the wiring, have you checked the car battery? A weak battery can cause weird electrical issues. Also, where is the siren located on that model? That might give you a clue where to start looking for a wiring issue.

Good point about the battery! I'll check that first thing. As for siren location, I'm not sure. Is there a common place they usually hide these things? Like under the hood, or maybe near a wheel well? If it's corrosion, I hope I can get to the wiring. I am not a mechanic, so if it goes beyond simple fixes I am at the end of my knowledge.

A low battery can cause the alarm to act up. Siren location varies, but under the hood near the firewall or inside a fender well are common spots. You could also try searching online forums specific to your model; someone's probably posted a diagram or photo. If you're not comfortable tracing the wiring, especially if it's buried deep, that 95€ quote is looking better. Sometimes it's cheaper to pay a pro than to break something else fixing it yourself. It could be a corroded connection, but they will check everything.

I checked the battery, and it seemed fine. Looked up the siren location, and it was buried deep. I admitted defeat and took it to the shop. Turns out, it WAS a corroded connector on the siren wiring, just like the error code suggested. 95€ later, the alarm is working perfectly again. Thanks for the help!