Siren (SCM/BBS)
The siren is used as a sound source for the alarm function. The siren is located in a protected position under the fender liner in the front right wheel housing. From and incl. structure week 201128 the siren is available in two versions, with or without internal vehicle inclination sensor. The type of siren installed in the vehicle depends on the market and the customer's wishes.
The siren sounds if the power supply to it is cut or if communication with the master electronic module (UEM/REM) fails while the alarm is activated. The siren contains an internal battery which is charged when the ignition is on or the engine is running. The battery service life is limited and depends on the local climate. The battery cannot be replaced by itself. Any alarm cause can be read from VADIS. This states what caused the alarm.
The siren is powered via a fuse from the central electronic module (CEM) The siren is grounded in the engine compartment.
There are diagnostics for the siren.
From and incl. structure week 201128 the siren on XC90 is connected to and communicates with REM instead of UEM.