VW Tiguan Alarm System Failure: Fix Communication Issues

Had the exact same fault detection issue with my 2015 VW Touareg diesel. As someone with moderate experience in car electronics, I initially tried basic troubleshooting, but the alarm controller remained completely dead. The signal problem turned out to be a damaged wire harness connector near the alarm siren unit. The security breach was triggered by water seepage that corroded the connection points. The workshop found this during their diagnostic scan when checking the alarm reset functionality. Total repair cost was 95€, which covered: Full diagnostic scan, Cleaning of connection points, Replacement of the faulty plug connector, System reset and testing The fix took about an hour and the alarm system has worked flawlessly since then. Would need to know more about your specific case though: Have you noticed any water damage or moisture in the vehicle? Does the alarm make any sound at all? When did the issue first appear? Have you had any recent work done near the alarm components? This information would help determine if you are dealing with the same root cause or if there might be a different issue at play.

Thanks for the detailed guidance. I had my last service at 38000km where they performed extensive diagnostics and confirmed no issues with the alarm system. Looking at the workshop invoice, they also checked all electrical systems. Two weeks after the service, I first noticed the signal problem during a routine alarm reset attempt. While the siren remains completely silent, other electrical systems work fine. After checking your suggestion, I did spot some moisture near the rear panel where the alarm siren is mounted. Based on your repair cost estimate, the 95€ seems reasonable if it is indeed the same wiring issue. Will have this checked at the workshop next week, focusing specifically on potential water damage to the alarm controller connections.

Thanks for those additional details about the timing of your alarm disarm problems. The fact that the issue started shortly after a full service where all electrical systems were checked is quite telling. In my case with the Touareg, I also had a fully functioning system during service checks, but the vehicle security started acting up soon after. The water seepage developing near the rear panel is a classic sign of the wiring issue I experienced. The location matches exactly where my corroded connections were found. One key difference worth noting, my alarm siren would occasionally make intermittent sounds before failing completely, while yours went straight to silent mode. However, given the moisture you spotted in the same critical area, the root cause is likely identical. The wiring connections in that section are particularly vulnerable to corrosion. A workshop diagnostic scan should quickly confirm if your alarm controller is experiencing the same connection failure. Based on the similarities in our cases, having them focus on the wire harness connector near the siren unit is a good starting point. Just make sure they thoroughly dry and protect the area after repairs to prevent future security breaches from moisture. Let us know what they find during the inspection next week.

Thanks for the helpful input. After reading about similar vehicle security issues, I am now confident about the repair direction. I just had the car inspected today and you were spot on, they found significant corrosion at the wire harness connector near the siren unit, causing the signal problem. The workshop quoted 110€ for the complete repair, including: New wiring harness connector, Waterproofing treatment, Full alarm reset and testing, Labor costs This is slightly more than what you paid but still reasonable given current prices. They can fix it tomorrow and promised the alarm controller will be fully functional again. They will also add extra moisture protection to prevent future wiring issues. Really appreciate all the feedback that helped pinpoint the exact problem area. Will update once the repair is complete to confirm if this resolves my alarm system troubles completely.