This is my first post on this forum so apologies if I haven't done everything quite right. I have a 2009 Mercedes C200 estate, W204 I believe, which has developed a false alarm issue. I've read lots of posts here and other forums regarding this issue, most of them pointing the finger of blame at the siren. I know it's not the anti-tow system, I've had a false alarm even when that was disabled before leaving the car. My local Mercedes dealer said they had never replaced a siren on one of these models however they do suffer from water ingress. Their advice was to check the connector for evidence of corrosion. I did and it was a clean as a whistle, I removed it anyway to eliminate it and to shut it up. For those of you that are trying this, the siren is behind the wheel lining of the passenger side (sometimes called the left hand side or here in the UK it's referred to as the nearside) front wheel. The lining is in two halves, it's behind the half closest to the passenger door not the one closest to the bumper. Removing the siren hasn't helped I'm still getting false alarms, no siren but flashing lights. It looks like the problem may well be down to door/tailgate /bonnet switches or movement detector within the cab. Does anyone know where these are located? Are any of these cheap fault code readers any use? My local dealer wants £96+vat just to plug my car into a diagnostic machine. Any help appreciated.