For those of you who remember "Stump the Chumps" section of Car Talk, this one is for you; 2004 d2 with 216,000 miles on it. Recently, the alarm system has decided to go rogue on me. When I lock the car the horn is sounding like I left a door open or something(nothing open). I walk away and two minutes later the alarm starts going off. I go out, shut it off via the fob. I get in and the alarm light is pulsing rapidly. No other issues.
Happens all the time now.
Anybody got any thoughts on this one?

 

One of the door sensors is my bet

 

The mislock signal (horn beep) is triggered if any of the five doors are not closed, or the bonnet is not closed and latched.

The door lock "sensors" are integral to the lock mechanisms. There are no separate sensors. I reviewed the Valeo BCU guide available at the Nanocom site but I did not find any way to diagnose where the fault may be among the five door locks.

The problem could also be a faulty bonnet switch. That can be tested easily by removing it and checking its continuity with the switch depressed, or by removing it and temporarily connecting its two wires with a jumper (e.g. a paper clip).

 

Or the hood switch

 

Isn't that what I wrote? Or are you taking exception to my use of the word bonnet instead of hood? 🙂

 

I've not played with nanocom. On my 04/05 Passat I can view all the door/trunk locks with vag-com. This makes finding a faulty actuator simple although they are usually accompanied by a door that either stays locked or stays unlocked despite what button you push.

Some report odd security system issues with water leaks under the dash, specifically around the fuse panel. Got any wet carpets after a heavy rain?

 

Does the fuel flap cause a mislock alarm if it's open?

 

Thank you for all the responses. Has anyone ever replaced the mechanism?

 

Some weird post lag going on...No issue with your use of bonnet.

 

When I was doing a little research yesterday for this topic, I found this reference in the RAVE Electrical Library.



There were no other references in the Electrical Circuits PDF or the Workshop Manual about the fuel flap being an input to the alarm system. The BCU uses alarm systems to include disabling the fuel flap solenoid as an output.