System Description/Design

System description/Design

General




The central locking system is a distributed system. Those parts which are included in the system are:
- rear electronic module (REM)
- central electronic module (CEM)
- driver door module (DDM)
- passenger door module (PDM)
- driver information module (DIM)
- climate control module (CCM)
- upper electronic module (UEM)
- switch for unlocking the fuel tank filler cover
- lock units in doors
- lock motor at the fuel tank filler cover
- lock unit for tailgate/trunk lid.

Rear electronic module (REM)




Rear electronic module (REM) (4/58) controls and monitors the central locking system and its functions. The control module is located under the protective panel on the left-hand side of the cargo compartment. No door or hatch can be unlocked without a command from the rear electronic module (REM). The rear electronic module (REM) continuously follows up the status of the system with respect to the status of door and lock motors. For further information, see Design and Function, rear electronic module (REM).
Rear electronic module (REM) is supplied with power from the ignition switch and is grounded in the body.

Central electronic module (CEM)




Central electronic module (CEM) (4/56) is located behind the dashboard, beside the driver. The function of the central electronic module (CEM) in the central locking system is:
- to activate the direction indicators, as confirmation with locking and unlocking the central locking
- to send a command, to activate the acoustic signal in the driver information module (DIM) with the function for key warning
- to send a message to the rear electronic module (REM), on the type of key used to unlock the vehicle or the type of key for switching on the ignition. This is significant for activating and deactivating private locking.
- to forward the request for unlocking the fuel tank filler cover from the light switch module (LSM).
Central electronic module (CEM) communicates with the rear electronic module (REM) via the low-speed side of the CAN network.
For further information, see Design and Function, central electronic module (CEM).

Driver door module (DDM) / passenger door module (PDM)




Driver door module (DDM) (3/126) is located in the driver's door and the passenger door module (PDM) (3/127) is located in the passenger door. Amongst other things, switches for window lifts are located on the top part of the control modules. The appearance and physical design differs between the two control modules.
The control panel on the driver's side has control buttons for setting the door mirrors and window lifts.
The control panel on the passenger side has control buttons for the power window mechanism.
Also on each front side door is a button for locking and unlocking central locking.
Driver door module (DDM) and the passenger door module (PDM) are directly connected to the lock unit in each door. Driver door module (DDM) and the passenger door module (PDM) lock and unlock the door on a command from the rear electronic module (REM). Driver door module (DDM) and the passenger door module (PDM) can only unlock the door after receiving a signal from the rear electronic module (REM).
Driver door module (DDM) and the passenger door module (PDM) have diagnostic functions which monitor the function of the buttons with respect to jammed buttons and relays.
Driver door module (DDM) and the passenger door module (PDM) communicate with the rear electronic module (REM) via the low-speed side of the CAN network.
For further information, see Design and Function, driver door module (DDM) and passenger door module (PDM).

Driver information module (DIM)




Driver information module (DIM) (5/1) displays a message in the text display and lights a warning lamp if one of the side doors or a hatch has opened during the journey. If the doors or hatches are fully closed then this is indicated by means of contact breakers in the lock units. A contact breaker at the hood is only fitted on vehicles with alarm.
A yellow warning lamp lights if the vehicle speed is below 7 km/h (5 mph). The red warning lamp lights if the vehicle speed is above 7 km/h (5 mph).
The tailgate is only indicated by a text message and yellow warning lamp, irrespective of the speed.
Driver information module (DIM) also displays a message with activation and deactivation of the functions private locking, child safety locks, and when the fuel tank filler cover is opened. The driver information module (DIM) also emits an acoustic signal with the function for key warning.
Driver information module (DIM) communicates with the rear electronic module (REM) via the low-speed side of the CAN network.
For further information, see Design and Function, driver information module (DIM).

Climate control module (CCM)




Climate control module (CCM) (3/112) receives the signals from the switches furthest down on the dashboard environment panel (7 in a row). Located here amongst other things are switches for private locking, child safety locks and reduced alarm.

Note! The switches may be arranged in a different order from the one shown in the illustration depending on the vehicle's configuration and equipment.

When one of the switches is pressed the climate control module (CCM) sends a request over the CAN network to the rear electronic module (REM) that the corresponding function is activated or deactivated.
The climate control module (CCM) communicates with the rear electronic module (REM) via the low-speed side of the CAN network.
For further information, see Design and Function, climate control module (CCM).

Upper electronic module (UEM)




Upper electronic module (UEM) receives the signals from the remote control and checks that the remote control belongs to the vehicle. For the upper electronic module (UEM) to be able to perform the check it must be programmed with codes for the remote controls belonging to the vehicle. If the key being used is approved then a request is sent for unlocking or locking to the rear electronic module (REM).
Upper electronic module (UEM) communicates with the rear electronic module (REM) via the low-speed side of the CAN network.
For further information, see Design and Function, upper electronic module (UEM).

Switch for unlocking the fuel tank filler cover




The switch for unlocking the fuel tank filler cover is located on the light switch module (LSM) (3/111). The switch is only on vehicles with fuel tank leakage diagnostics.
Light switch module (LSM) communicates in serial with the central electronic module (CEM). If the switch is pressed the central electronic module (CEM) sends a request to the rear electronic module (REM) that the lock motor for the fuel tank filler cover is activated. The cover can be opened if the speed of the vehicle is less than 7 km/h (5 mph).
The fuel tank filler cover is opened after a delay so that the automatic check for fuel leakage can be interrupted and the fuel tank pressure equalized. The fuel tank filler cover is then locked when the vehicle reaches a speed of 16 km/h (10 mph) or after 10 minutes if the vehicle has 2 stage locking function.

Lock units side doors




The lock units (3/74-77) are fitted in the rear of the side doors. The lock units in the front doors are each directly connected to their associated control module in the door. The lock units in the rear doors are directly connected to the rear electronic module (REM).
There are different versions of the lock units, depending on the configuration of the lock motors.
There are two versions of the lock units in the front doors with lock motors for:
- central locking
- central locking and deadlocking.
There are four versions of the lock units in the rear doors with lock motors for:
- central locking
- central locking and deadlocking
- central locking, deadlocking and child-proof locking
- central locking and child-proof locking.
The central locking lock motor locks the door.
The deadlocking lock motor disconnects the mechanical couplings from the door handles and the lock button to the lock unit. This function depends on the market.
The lock motor for child safety locks is only for the rear doors and disconnects the inner door handle and the lock button.
Driver door module (DDM) and the passenger door module (PDM) can only unlock the doors after a command from the rear electronic module (REM).
In addition to the lock motors, the lock units contain up to three contract breakers depending on the configuration:
- contact breaker to indicate that the central locking motor is in the locked position
- contact breaker which indicates that the door is not locked
- contact breaker to indicate the child-proof lock motor is locked.
The lock motors have integral overheating protection which prevents lock motor activation if the lock motor risks becoming too hot.

Lock unit, tailgate/trunk lid





Applicable to the S80/S60:
The lock unit in the trunk lid on the S80/S60 actually has no "unlocked" mode. The difference between locked and unlocked mode is whether or not the rear electronic module (REM) activates the lock unit when the switch in the trunk lid is pressed. Opening the trunk lid depends on whether central locking is in unlocked mode or not. There is a lock cylinder in the trunk lid as a mechanical reserve alternative. The lock cylinder is mechanically connected to the lock unit. The trunk lid can be opened via the lock cylinder with the key.

Applicable to the V70/XC70/XC90:
The lock unit in the tailgate locks and unlocks during a normal locking procedure. When the tailgate is unlocked and the handle on the tailgate is pressed the catch in the mechanism from the lock brace in the body disengages and the tailgate opens.
There is a lock cylinder on the tailgate on the V70/XC70 if an auxiliary rear facing seat was fitted at the factory. The tailgate can be unlocked with a key using the lock cylinder.
There is a lock cylinder on the tailgate on the XC90 if a third row of seats was fitted at the factory.
The tailgate/trunk lid can also be unlocked/opened separately with a special button on the remote control.
The switch on the trunk lid (S60/S80) and lock unit (3/78) are directly connected to the rear electronic module (REM).

Remote control




The remote control is used to activate function in the system remotely. The basic functions of the remote control are:
- unlocking
- locking
- unlocking the trunk lid/tailgate
- activating the local lighting
- activating alarm functions.
The remote control has an integrated communication circuit and memory. When a button on the remote control is pressed a coded signal is sent out. This signal is received by the upper electronic module (UEM) and is forwarded to the rear electronic module (REM). In order that the remote control can work with the system a unique code must be programmed into the remote control by the upper electronic module (UEM). This is first performed at the factory. Following which remote controls can be added or removed at a Volvo workshop.
The remote control has an integral battery which is used when commands are sent to the system. This battery requires replacement at regular intervals. An indication of a weak battery is when the range of the remote control decreases.