System Description/Design

System description/design

General

The central locking system is a distributed system. Those parts which are included in the system are:
- central electronic module (CEM)
- driver door module (DDM)
- passenger door module (PDM)
- right rear door module (RDM) (not C30/C70)
- left rear door module (LDM) (not C30/C70)
- driver information module (DIM)
- phone module (PHM)
- infotainment control module (ICM)
- convertible Roof Module (CRM) (only C70)
- switch for valet locking
- switch for unlocking the fuel tank filler cover
- lock motor units in the doors
- lock motor at the fuel tank filler cover
- lock motor for the trunk lid/tailgate
- remote control receiver
- supplemental restraint system module (SRS)
- indicator LED in the doors (only C70)
- lockable storage compartment (only C70)
- lock for ski hatch (only C70).

Central electronic module (CEM)




The central electronic module (CEM) (4/56) controls and monitors the central locking system and its functions. No door can be unlocked without a command from the central electronic module (CEM). Most of the system settings are stored in the central electronic module (CEM). Many of these settings are market dependent. For information about the settings which can be made, see: Diagnostic functions Diagnostic Functions
The central electronic module (CEM) continually checks the system to monitor the status of the doors and lock motors. For further information, see Design and Function, central electronic module (CEM).

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




The driver door module (DDM) (3/126) and passenger door module (PDM) (3/127) are identical in appearance. The only difference between the two units are the software downloaded into them after installation in the vehicle. There are also different control panels connected to the control modules. The side on which each control panel will be positioned is determined by whether the vehicle is left or right-hand drive. The door control modules communicate with the central electronic module (CEM) via the low speed side of the CAN network.
The control panel on the driver's side has control buttons for adjusting the door mirrors, window lift mechanisms and the button for activating child-proof locking (not C70).
The control panel on the passenger side has control buttons for the power window mechanism.
There is also a button for locking and unlocking the central locking by the inner door handle on each side.
The door control modules are directly connected to the lock unit in each door. The door control modules lock and unlock the door on receipt of a command from the central electronic module (CEM). The door control modules can only unlock the door on receipt of a signal from the central electronic module (CEM).
The following only applies to the S40/V50:
The driver door module (DDM) and passenger door module (PDM) communicate with the control module in the rear door on the same side of the vehicle via a serial interface (LIN).
The door control modules forwards the received signals from the CAN network to the rear door control module. The signals forwarded are the locking and unlocking commands. The door control modules also forward signals from each rear door control module on the CAN network. The signals that are forwarded indicate the position of the lock motors for child-proof and central locking.
The door control modules have diagnostic functions which monitor the function of the buttons to check that they have not stuck and that the relays are intact.
For further information, see Design and Function, door control modules.

Control modules in the rear doors





Note! This section only applies to the S40/V50.

The control modules in the rear doors are always referred to as the left rear door module (LDM) (3/128) and right rear door module (RDM) (3/129). This is different from the front door control modules which are designated driver door module (DDM) and passenger door module (PDM).
The control modules also have control panels for the window lift mechanisms.
The rear door control modules use serial communication with the front door control module on the same side of the car.
The rear door control modules are directly connected to the lock motor in each door. The door control modules lock and unlock the door on receipt of a command from the front door control module.
The rear door control modules forward the status of the lock motors for child-proof and central locking to the relevant front door control module.
For further information, see Design and Function, door control modules.

Driver information module (DIM)




The driver information module (DIM) (5/1) displays a text message and lights a warning lamps if any of the side doors or tailgate/trunk lid or hood have been opened whilst driving. A micro-switch indicates that the doors or tailgate/trunk lid are fully closed. Only cars with an alarm have a micro-switch at the engine hood.
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.
For further information, see Design and Function, driver information module (DIM).

Phone module (PHM)




Phone module (PHM) (16/60) is an option. The phone module (PHM) communicates with the central electronic module (CEM) via the low speed side of the CAN network. If a phone module (PHM) is installed, the unit can be used for remote unlocking via the Volvo On Call service. This means that the vehicle can be unlocked from a Volvo Service Center.
The phone module (PHM) can also automatically transmit an emergency signal if one or more airbags have been triggered. The emergency signal is also transmitted if the "SOS" button is pressed.
For further information about the phone module (PHM), see Design and Function, phone module (PHM).

Infotainment control module (ICM)




The customer can personalize some of the central locking settings using the infotainment control module (ICM) (16/1). The infotainment control module (ICM) communicates with the central electronic module (CEM) via the low speed side of the CAN network. The central locking settings are presented via a menu system in the display on the infotainment control module (ICM). For further information about the settings which can be made, see: Diagnostic functions Diagnostic Functions
The central locking settings are stored in the central electronic module (CEM) and are transmitted to the infotainment control module (ICM) when the ignition is switched on.
For further information, see Design and Function, infotainment control module (ICM).

Switch for valet locking (not C30/V50)




The switch for valet locking is at one edge of the glove compartment in the dashboard. The switch is directly connected to the central electronic module (CEM). The switch is affected after the glove compartment has been locked in the normal way using the key blade (turning 0 to 90 degrees) and then continuing to turn (from 90 to 180 degrees). Applies to the C70: Valet locking also includes lockable storage compartments and the lock for the ski hatch.

Switch for unlocking the fuel tank filler cover




The switch for unlocking the fuel tank filler cover is on the light switch module (LSM) (3/111). The switch is directly connected to the central electronic module (CEM). The cover can be opened if the vehicle speed is below 7 km/h (5 mph).
For the American market, the function has a delay before the fuel tank filler cover can be opened. This is to allow for the cancellation of the automatic leak test and for the pressure in the tank to even out.

Lock units side doors





Note! The C30 and C70 only have the front locking units.

The lock units are installed in the doors and are directly connected to the door control module in the relevant door.
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.
The locking units in the rear doors (only applies to the S40/V50) are available in four versions with locking 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 deadlock lock (BLL) motor disengages the inner lock button (only C30/S40/V50) and the inner door handle.
The child-proof lock motor is only for the rear doors (only S40/V50) and disengages the inner door handle.
The door control modules can only unlock the doors on receipt of a command from the central electronic module (CEM). 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 to indicate that the door is in the latch position (not fully closed)
- contact breaker to indicate the child-proof lock motor is locked (only S40/V50).
The lock motors have built in overheating protection which prevents the motor from activating if there is a risk of the motor getting too hot.

Lock motor tailgate/trunk lid

C30/S40/V50





C70




In practice there is no "locked" position for the lock on the tailgate/trunk lid. The difference between locked and unlocked is whether the central electronic module (CEM) will activate the lock motor or not when the switch on the tailgate/trunk lid is pressed.
The tailgate/trunk lid is "locked" and "unlocked" at the same time as other doors if an unlock command is received from the remote control. The tailgate/trunk lid can also be unlocked separately using a dedicated button on the remote control.
For C70 it is also possible to unlock and open the tailgate using a lock cylinder which is located on the rear seat's left leading edge.
This lock is mechanically directly connected to the cargo compartment's locking mechanism.
The switch on the tailgate/trunk lid and lock motor (3/78) is directly connected to the central electronic module (CEM).

Remote control




The remote control is used to activate function in the system remotely. The basic functions of the remote control are:
- unlocking and locking the side doors
- unlocking the trunk lid/tailgate
- activating the local lighting
- activating alarm functions
- for the C70: unlocking and locking the storage compartment and ski hatch.
The remote control has a built-in communication circuit and a memory. A coded signal is sent when a button on the remote control is pressed. This signal is received by the remote receiver (RRX) and forwarded to the central electronic module (CEM). For the remote control to work with the system, a unique code in the remote control must be learned by the central electronic module (CEM). This takes place during installation at the factory.
The remote control has a key blade which is normally retracted inside the remote control. The key blade can be used in emergency situations to unlock the driver's door. This does not disarm alarm functions however, so should only be used as a last resort to open the car.
The remote control has an integrated battery which is used when commands are sent to the system. This battery must be replaced regularly. The remote control contains an internal voltmeter that measures the voltage of the internal battery. If the battery voltage is low, this information is transmitted in the messages transmitted to the Remote Receiver Module (RRX). The Central electronic module (CEM) receives this information and transmits a message via the CAN network to the Driver information module (DIM), which, in such cases, displays a message that the voltage for the remote control is low. Reduced remote control range is also an indication that the battery charge is low.

Note! It has been shown that in some cases there is a system function fault when communication between the Remote Receiver Module (RRX) and the ignition key are affected for different reasons. The function fault is not due to any electrical fault and no diagnostic trouble codes (DTCs) are stored either.

Due to increased external radiation, for example from TV/radio transmitters and mobile telephones, the signal from the remote control can, on rare occasions, be jammed. This is a rare fault but it can occur, especially in places where different external signals can impair transmitting and reception conditions. This is not only associated with the central locking system but can also affect different types of wireless communication.

Remote Receiver Module (RRX)




Remote Receiver Module (RRX) is located up at the headlining, to the left of the front lighting panel.
Remote Receiver Module (RRX) receives signals sent from the remote control and transmits them on to Central electronic module (CEM) via serial communication (ISO).
When a key is in the ignition the Central electronic module (CEM) ignores all messages that come from the Remote Receiver Module (RRX). This is so that, e.g., the central locking system will not be locked if a button on the remote control is pushed accidentally.
The remote receiver checks for a signal from a remote control 4 times a second.
Remote Receiver Module (RRX) is supplied with voltage directly via 30-feed and is grounded in the A-pillar.

Lockable ski hatch (only C70)




The vehicle is equipped with an electric lock for the ski hatch to prevent access to the cargo compartment when the roof is open. Locking/unlocking of the ski hatch is controlled by the Convertible Roof Module (CRM) (4/59).

Lockable storage compartment (only C70) (option)




The vehicle can be equipped with 4 electrically lockable compartments. Two compartments are located in each door and two compartments are in each side of the rear seat. The compartments are locked and unlocked at the same time as the ski hatch lock and are controlled by the Convertible Roof Module (CRM).