Design

Design

Rear electronic module (REM)




The rear electronic module (REM) is the main unit for alarm functions.
The control module communicates with units that are connected directly or serially and via CAN communication. The control module has a number of sensors connected to it and carries out the appropriate actions depending on the status of the sensors and input signals from other control modules.
For more information, see Design and Function, Rear Electronic Module (REM).

Switches in the lock units




A switch is fitted in each lock unit for the doors and trunk lid/tailgate. Vehicles equipped with an alarm have a switch in the hood lock. The switches are closed when the respective door or hatch is closed. There is no switch for the fuel tank filler cover.
At regular intervals, the rear electronic module (REM) checks if the switches are closed when the alarm is activated. If the rear electronic module (REM) detects that a switch opens, the alarm is triggered.
If the rear electronic module (REM) detects a switch that is not closed when central locking is engaged and alarm activation is to be carried out, the inclination sensor module (ISM) and the mass movement sensor module (MMS) will not be activated. Similarly, signals from a switch that was not closed during activation will be disregarded. No flash is given in acknowledgement before all switches are closed.

Siren control module (SCM)




The siren is used as the acoustic source for the alarm function. The siren is located in a protected position under the fender liner in the right front wheel housing.
The siren begins to sound if the power supply is cut or if communication with the upper electronic module (UEM) stops when the alarm is activated. The siren has an internal battery that is charged when the ignition is switched on. This battery can complete approximately 10 alarm cycles and has a limited service life depending on the climate in which it is used. The battery cannot be replaced as a separate component. The cause of the alarm can be read off and verified via VIDA.
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 (SCM).

Mass movement sensor module (MMS)




The mass movement sensor module (MMS) is located in the roof under its own panels. There is one mass movement sensor module (MMS) in the S60/S80/V70/XC70. The sensor is located in the center of the roof.
The two sensors in the XC90 are located along the front edge of the roof and in the roof above the cargo compartment.
The mass movement sensor module (MMS) is used to detect movement in the passenger compartment when the alarm is activated.
When the alarm is activated, the upper electronic module (UEM) carries out a check of the sensors.
The sensors communicate serially with the upper electronic module (UEM). If two sensors are installed, these are connected in parallel to the upper electronic module (UEM).
When the sensors are activated, they transmit microwaves into the vehicle. The microwaves bounce back from the interior of the vehicle and the sensors react to variations in the rebounding waves. A system that uses microwaves is more stable than a system that uses ultrasound sensors and reduces the number of false alarms. For example, microwaves are not affected by the changing temperature of different layers of air inside a vehicle parked in the sun. If the vehicle is exposed to outside microwave interference, a false alarm may be triggered. The cause of the alarm can be read off and verified via VIDA.
The mass movement sensor module (MMS) is powered and grounded via the upper electronic module (UEM).

Inclination sensor module (ISM)




The inclination sensor module (ISM) is fitted near the rear electronic module (REM) and gives input signals to the rear electronic module (REM) when the alarm is activated. The sensor registers changes in the vehicle angle that would occur during an attempted tow or theft of a wheel, for example. The inclination sensor module (ISM) is connected in series with and powered by the rear electronic module (REM). The inclination sensor module (ISM) is grounded to the body. The cause of the alarm can be read off and verified via VIDA.

Glass breakage sensors




Glass breakage sensors in the rear side windows and rear window are installed only in the V70/XC70, which is also equipped with a mass movement sensor (MMS). The glass breakage sensors are used to detect a broken rear window around the cargo compartment. The glass breakage sensors in the side windows are connected in series. The glass breakage sensor in the rear window is connected in series to the switch in the tailgate lock unit that indicates an open tailgate. When the alarm is activated, the rear electronic module (REM) checks that the connection is intact at regular intervals. Should an open circuit occur due to a broken window or opened tailgate, the rear electronic module (REM) triggers the alarm. The cause of the alarm can be read off and verified via VIDA.

Alarm LED




The alarm LED is located on top of the dashboard in the same shell as the sun sensor and twilight sensor. The LED is directly connected to the rear electronic module (REM) and is used for indicating alarm status.
When the alarm is activated, the LED will flash approximately once every two seconds.
If the alarm is triggered, the LED will begin to flash rapidly (approximately 5 times per second) and continue to flash as long as the alarm continues. Once the alarm cycle is concluded, the LED will once again begin to flash slowly.
If the alarm has been triggered, the LED will begin to flash rapidly again (approximately 5 times per second) after the vehicle is unlocked until the ignition is switched on. This is an indication to the driver that the alarm has been triggered.

Switch for reduced alarm





Note! The switches can be positioned in a different order than indicated in the illustration depending on vehicle configuration and equipment.

The switch for reduced alarm is located on the climate control comfort panel. The switch is used to temporarily deactivate the inclination sensor module (ISM) and mass movement sensor module (MMS) functions. When the function is activated, deadlock mode will not engage after the vehicle is locked. The function can only be activated when the ignition is in position I, 0 or after the ignition has been switched off and up to one minute after the ignition key has been removed from the ignition switch.
The switch has an integrated LED that indicates if the function is activated and messages will be displayed in the driver information module (DIM). However, messages are not displayed once the key is removed.
The alarm can be put into garage mode using the switch. This mode is engaged if the switch is depressed and the remote control unlocking button is depressed within 5 seconds. In garage mode, automatic alarm functions will not be activated. This mode is engaged for 24 hours after activation.