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 and the mass movement sensor module (MMS), or movement sensor (IMS), 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 (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.

Mass movement sensor module (MMS)





Note! For XC90 MY 2012- the Mass movement sensor module (MMS) is replaced with ultrasonic sensor module (IMS).

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. 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).

Ultrasonic sensor module (IMS) (Only XC90 MY 2012-)




The ultrasonic sensor module (IMS) is located in a cover in the ceiling. The ultrasonic sensor module (IMS) is used to detect movements inside the passenger compartment when the alarm has been activated. The aim is to detect anyone trying to reach in and steal a bag or similar or example. When the sensor is activated, an internal self test is performed and informs the Central electronic module (CEM) of the result. If the test failed the Central electronic module (CEM) stores a DTC. The sensors communicate serially and are powered via the Upper electronic module (UEM). When the sensor is activated it transmits ultrasound inside the passenger compartment. The sound waves reflect back to the sensor and if the sensor detects a change in reflections or movements in the passenger compartment, the alarm is tripped.

Note! The sensor's performance is affected by air turbulence and therefore all windows and any roof hatches must be closed for the sensor to work optimally.

Inclination sensor module (ISM) (structure week -201127)




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.

Inclination Sensor Module alarm (BBS-IS) (XC90 structure week 201128-)




If the vehicle is equipped with a vehicle inclination sensor, the sensor is integrated in the siren. The vehicle inclination sensor reacts to changes in the angle of lean of the vehicle and transmits a signal to the Rear electronic module (REM). While the vehicle inclination sensor is mounted in the siren it is counted as a separate unit. If the vehicle inclination sensor indicates that the vehicle is being lifted the Rear electronic module (REM) must send an activation signal to the siren. In this case the siren cannot trigger an alarm by itself.
The siren is powered via a fuse from the central electronic module (CEM) The siren is grounded in the engine compartment.

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 and mass movement sensor module (MMS) alternatively ultrasonic sensor module (IMS) 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.
With the switch the alarm can be set to so called garage mode if the car is configured for passive activation (option for certain markets). This mode is activated if the switch is pressed in and the unlock button on the remote control is pressed in within 5 seconds. In garage mode there will be no passive activation of the alarm. This mode is active for 24 hours after activation or until any button is pressed on the remote control.