The vol sensor detects internal movement, triggers alarm. Not functional (in terms of triggering alarm) when running.
We've had the "Quality of official documentation" discussion ad nauseum in other threads. You can open the bonnet with system "unlocked" and doors not opened. The sensor is active in some capacity as I've had to trace a fault in a system where the sensor was faulty and triggering horn on attempt to lock. Replace, went away. Sit in car waving at it. Duplicate result. Basic scientific process.

