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)
- left rear door module (LDM)
- driver information module (DIM)
- phone module (PHM)
- Infotainment control module (ICM)
- switch central locks for locking and unlocking doors
- switch for valet locking
- switch for opening the fuel tank filler cover (on the light switch module (LSM))
- switch for unlocking the trunk lid (on the light switch module (LSM))
- lock units in doors
- lock motor at the fuel tank filler cover
- lock motor for the trunk lid/tailgate
- Remote Receiver Module (RRX) (Remote Keyless Entry (RKE) for the Japanese market)
- supplemental restraint system control module (SRS).

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.

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 middle speed side on the CAN-net (MS CAN).
The control panel on the driver's side has switches for locking and unlocking as well as lock indication of the central locks via LED, for adjusting the door mirrors, operating the window lift mechanisms and switches for activating the child-proof locks, if installed. The driver's panel can also have switches for activating electric folding mirrors. The switch for locking and unlocking as well as lock indication of the central locks via LED is directly connected to the driver door module (DDM) while the other switches on the panel are connected in series via LIN.
The control panel for the passenger side has a control button for window lift. Some vehicles also have a switch for locking, unlocking as well as lock indication of the central locks via LED The switch for locking and unlocking of central locks and control button for window lift are directly connected to Passenger door module (PDM).
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 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.
The control modules are powered via the rear fuse box and grounded in the body.
For further information, see Design and Function, Driver door module (DDM)/passenger door module (PDM).

Control modules in the rear doors




The control modules in the rear doors are designated the left rear door module (LDM) (3/128) and right rear door module (RDM) (3/129). The control modules 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.
Some vehicles (option as well as market-dependent) have lock buttons by the rear doors, with lock indication, for local locking and unlocking.
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.
The control modules are powered via the rear fuse box.
For more information, see: Design and Function - Driver door module (DDM)/passenger door module (PDM).

Driver information module (DIM)

Location Of Components:

The driver information module (DIM) (5/1) displays a text message and lights a warning lamp 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 contact breaker 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.

The driver information module (DIM) shows the message in its displays if:
- the driver's door is opened and the vehicle is in ignition position I-III. The display shows what needs to be done to switch off the ignition
- if the gear selector is not in position P and an attempt is made to remove the remote key form the starter module
- the electrical child-proof lock is activated or deactivated
- valet locking of the glove compartment and cargo compartment is activated or deactivated
- the remote key transmits a warning to the vehicle about low battery voltage for the remote key.
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 middle-speed side of the CAN network (MS CAN). 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) (3/281). The Infotainment control module (ICM) communicates with the central electronic module (CEM) via the middle-speed side of the CAN network (MS CAN). 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 (option, market dependent)




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). When activating or deactivating the function, a message is displayed in the driver information module (DIM).

Switch for opening the fuel tank filler cover




The switch for opening the fuel tank filler cover is on the light switch module (LSM) (3/111). The light switch module (LSM) is serially connected to the central electronic module (CEM) via LIN. 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




The lock units (6/36, 6/55-57) are 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 (BLL) (market-dependent).

There are four versions of the lock units in the rear doors with lock motors for:
- central locking
- central locking and deadlocking (BLL) (market-dependent).
- central locking, deadlocking (BLL), and child-proof locks (market-dependent) (option)
- central locking and child-proof locking (option).
The central locking lock motor locks the door.
The deadlock lock motor (BLL) disengages the inner door handle.
The child-proof lock motor is only for the rear doors 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 which indicates that the door is not locked
- contact breaker to indicate the child-proof lock motor is locked.
To prevent the lock motors from becoming too hot, there is a protection function in the software in the central electronic module (CEM). The central electronic module (CEM) has a counter that counts a number of steps each time a central locking command is carried out. (The number of steps is determined by several parameters.)
The counter has a maximum value of 240 steps. Normally there are 12-13 activations in a row before the counter reaches the maximum value. The counter counts down by 1 step/second. If the counter has reached the maximum value, the central electronic module (CEM) will not perform commands for locking the central locking. The unlocking command will always be accepted, even if the maximum value has been reached. This means that if the central locking has been activated so many times that the counter has reached its maximum value, it will take about 5 seconds before the next central locking command is performed. The counter is fully restored after 4 minutes.
There is corresponding protection for the power child-proof lock motors

Lock motor tailgate/trunk lid




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 is "locked" and "unlocked" at the same time as the other doors if an unlock command is received from the remote key. The tailgate can also be unlocked separately with a special button on the remote key or via switch on Light switch module (LSM). There is also a function for activating the lock motor via the remote key or switch on Light switch module (LSM).
The switch on the tailgate/trunk lid and lock motor (6/8) is directly connected to the central electronic module (CEM).

Remote key




The remote key is used to activate functions in the system remotely. The remote key has buttons for activating the following functions:
- unlocking and locking the side doors
- unlocking the trunk lid/tailgate
- activating the local lighting
- activating alarm functions.
Internally, the remote key consists of two parts:
- transponder
- function for remote control.
The transponder is a communication circuit in the head of the key. The transponder has a unique identification code which connects the remote key to the vehicle. The transponder is coded. This code must be learned by the central electronic module (CEM) before the remote key can be used to start the vehicle. Once the transponder has been programmed for one vehicle, it cannot be programmed for another.
The remote key has a built-in communication circuit and a memory. A coded signal is sent when a button on the remote key is pressed. This signal is received by the Remote Receiver Module (RRX) receiver and forwarded to the central electronic module (CEM). For the remote key to work with the system, a unique code in the remote key must be learned by the central electronic module (CEM). This takes place during installation at the factory.
The remote key has a key blade which normally is inserted in the remote key. The key blade can be used in an emergency to lock and unlock the driver's door and to activate emergency locking in the other doors. However, these actions do not deactivate installed alarm functions which means that this shall be seen as a second alternative for locking or unlocking the vehicle.
The remote key has an integrated battery which is used when commands are sent to the system. This battery must be replaced regularly. The remote key contains an internal voltmeter that measures the voltage on the internal battery. If the battery voltage becomes too low, information about this is transmitted in the messages 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 shows a message that the voltage for the remote key battery is too low. Reduced remote key range is also an indication that the battery charge is low.

Note! In certain cases malfunctions may occur in the system when communication between the Remote Receiver Module (RRX) and the remote key is interrupted for different reasons. Malfunctions are not due to any electrical faults and do not generate any diagnostic trouble codes (DTCs). Due to increased ambient radiation, for example, from TV/radio transmitters and mobile phones and meters with remote reading, the signal from the remote key can, in some cases, be interrupted. In many cases this occurs in certain locations, where different outside signals make transmission and reception conditions unfavorable. This affects not only central locking systems but all types of wireless communication.

Remote Receiver Module (RRX)




The Remote Receiver Module (RRX) is mounted in the middle of the headlining above the rear seat.
The remote receiver module (RRX) is connected to the central electronic module (CEM) via serial communication (LIN). The remote receiver module (RRX) receives the signals transmitted from the remote key and forwards them to the central electronic module (CEM). When a remote key is in the starter module, the central electronic module (CEM) ignores all messages from the Remote Receiver Module (RRX). This prevents the central locking system from locking if a button on another remote key is unintentionally pressed in.
The remote receiver module (RRX) checks for a signal from a remote key approximately 6 times per second.
The receiver is powered from the central electronic module (CEM) and grounded in the body.

Note! The market in Japan has Remote Keyless Entry (RKE) regardless of if the vehicle is equipped with keyless entry system or not. When the vehicle is not equipped with keyless entry system, the Remote Keyless Entry (RKE) communicates directly with Central electronic module (CEM). If the vehicle is equipped with keyless entry system, the Remote Keyless Entry (RKE) communicates via Keyless Vehicle Module (KVM).