Hi, I had a Passat that the alarm was going off at random.
I think it's Central Conv. - 46.
Go into Measuring Blocks, open up the Label File and it will tell you the MB's to view to find the cause of the last 4 or 6 alarm triggering events.
Mine was the bonnet switch every time, which turned out to be corroded multiplug in passenger footwell.

There are no DTC's maybe because it thinks the alarm is doing its job and being triggered?

HTH, Martin.