System Description/Design
System description/Design
General
The central locking system with keyless functionality is a distributed system. The components of the system are:
- central electronic module (CEM)
- keyless vehicle module (KVM)
- 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 keyless entry (RKE) 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 which is part of the central locking system 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).
Keyless vehicle module (KVM)
The keyless vehicle module (KVM) controls keyless entry to the vehicle. The system allows the vehicle to be opened without inserting a key in the lock or pressing a button on the remote control. The control module is under the left front seat. The keyless vehicle module (KVM) works together with the central electronic module (CEM) when opening and starting the vehicle. The two control modules communicate via the low speed side of the controller area network (CAN) (LS-CAN).
There are a number of components in the keyless entry system:
- keyless vehicle module (KVM)
- antennas in the external door handles and in the rear bumper
- antennas in the passenger compartment and cargo compartment
- quick lock motors connected to the standard lock motors
- switches in door handles, locking buttons and additional lock motors
- Remote Keyless Entry (RKE) for signals from the keyless remote control
- remote control including keyless entry function.
If one of the external door handles is pulled outwards, the keyless vehicle module (KVM) activates the antennas in the handles on that side. A message is transmitted from the antennas. The purpose of this message is to check whether there is a remote control with keyless functionality in the vicinity of the vehicle. The remote control responds to Remote Keyless Entry (RKE) that forwards information to the Keyless vehicle module (KVM). If a remote control is found, the Keyless vehicle module (KVM) controls the remote control's identity. If the remote control is programmed for use in the vehicle, the keyless vehicle module (KVM) will activate the quick lock motor to open the door on which the handle was pulled out. At the same time, the keyless vehicle module (KVM) transmits a signal to the central electronic module (CEM) indicating that the key is authorized and that the other doors can be unlocked.
Note! During locking, the keyless vehicle module (KVM) only checks the quick lock motors in the doors. The other lock motors and the other functions in the central locking system are checked by the 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 (LS_CAN).
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.
The Driver information module (DIM) also displays a message if a passive key cannot be found when a start attempt is carried out or if a remote control that is used to start the vehicle cannot be found after the driver's door has been opened and closed. For further information regarding start functions, see Design and Function, Electronic immobilizer/Start inhibition.
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 (LS_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) (16/1) and the keyless entry system. The infotainment control module (ICM) communicates with the central electronic module (CEM) and keyless vehicle module (KVM) via the low speed side of the CAN network (LS_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 settings for the central locking system are stored in the central electronic module (CEM). The settings for the keyless entry system are stored in the keyless vehicle module (KVM). Information from both control modules is 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 (3/74-77) 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 four versions of the lock units in the front doors with lock motors for:
- central locking
- central locking and deadlocking
- central locking and quick locking
- central locking, deadlocking and quick locking.
The locking units in the rear doors (only applies to the S40/V50) are available in eight versions with locking motors for:
- central locking
- central locking and deadlocking
- central locking and child-proof locking
- central locking, deadlocking and child-proof locking
- central locking and quick locking
- central locking, deadlocking and quick locking
- central locking, child-proof locking and quick locking
- central locking, deadlocking, child-proof locking and quick 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 quick lock motor is hardwired to the keyless vehicle module (KVM) and opens the door upon receipt of a command from the keyless vehicle module (KVM).
Note! Quick locking is controlled entirely by the keyless vehicle module (KVM).
The door control modules can only activate the lock motors 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 (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.
When the quick locks are activated by the keyless vehicle module (KVM), the catches in the standard lock units are released from the striker plates in the car body. The quick locks contains a switch which is acted on by a control arm from the door handle. This switch is closed when the door handle is pulled out fully. This switch must be closed for the keyless vehicle module (KVM) to activate the quick lock. For further information, see Design and Function, keyless vehicle module (KVM).
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 or if the vehicle is unlocked passively. The tailgate/trunk lid can also be opened separately using a dedicated button on the remote control.
For the C70, it is also possible to unlock and open the cargo compartment using a lock cylinder, which is located under the cup holder in the centre console (model year 2006 and early 2007 versions). For the C70 (late versions 2007-), the lock cylinder is located on the left-hand front edge of the rear seat.
This lock is mechanically directly connected to the cargo compartment's locking mechanism.
The switch on the tailgate or trunk lid is directly connected to the keyless vehicle module (KVM) and to the central electronic module (CEM). This connection reduces the reaction time from the switch being pressed to the trunk lid or tailgate opening. If the vehicle is locked and the switch pressed in, the keyless vehicle module (KVM) activates the antenna in the bumper and begins checking for an authorized key. If an authorized key is found, the keyless vehicle module (KVM) transmits a signal to the central electronic module (CEM) to activate the lock motor in the trunk lid or tailgate. The lock motor (3/78) is directly connected to the central electronic module (CEM).
Remote control
Note! The remote control looks the same, irrespective of whether it supports keyless functionality or not. Check that the remote control is the correct type before programming it for the system. If an incorrect remote control is used, the keyless functions will not work.
The remote control can be used to activate system functions at a range of up to approximately 20 meters. The basic functions of the remote control are:
- unlocking the vehicle
- locking the vehicle
- unlocking the trunk lid/tailgate
- activating the local lighting
- activating alarm functions
- for the C70: unlocking and locking the storage compartment and ski hatch.
Internally, the remote control consists of three sections:
- transponder
- function for remote control
- function for the keyless entry system, if applicable.
The transponder is a communication circuit in the head of the key. The transponder has a unique identification code which connects the key to the vehicle. The transponder is coded. This code must be learned by the central electronic module (CEM) before the key can be used to start the vehicle when the key is in the ignition switch. Once the transponder has been programmed for one vehicle, it cannot be programmed for another.
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 a remote keyless entry (RKE) receiver and is forwarded on to the keyless vehicle module (KVM). For the remote control to work with the system, a unique code in the remote control must be learnt by the keyless vehicle module (KVM). This takes place during installation at the factory.
The keyless entry system is used for:
- unlocking
- locking
- passive starting
- passive key warning.
The circuits in the remote control which control the function for the keyless entry system are coded. The keyless vehicle module (KVM) must learn these codes for communication to function. This takes place during installation at the factory.
Normally two keys are programmed for the key on delivery. Additional keys can be added afterwards.
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, 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! There have been some cases of system malfunctions when communication between the Keyless Vehicle Module (KVM) and the ignition switch has experienced interference for various reasons. These malfunctions are not due to electrical faults and will not generate a diagnostic trouble code.
1. If the ignition key is held in the same hand that is used to turn the starter, the ignition key may not be identified correctly. This will display an error message in the Driver Information Module (DIM). The vehicle will not start either. The vehicle will start, however, if the starter is turned to 0 and a new starting attempt is made. The fault will not generate a diagnostic trouble code. This fault is rare.
2. If a button on the remote control is pressed when the Keyless Vehicle Module (KVM) attempts to read the identity of the ignition key, the reading will fail. This is because the ignition key cannot not transmit and receive data at the same time (pressing a button on the remote control will mean the ignition key is engaged in transmitting a "normal" remote control command). This fault could occur if the key is kept in a pocket or bag and a button is pressed by mistake.
3. 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 particular places where different external signals can impair transmitting and reception conditions. This is not only associated with keyless systems but can also affect different types of wireless communication.
Remote keyless entry (RKE) receiver
The remote keyless entry (RKE) receiver is installed above the headlining to the left of the front lighting panel. The receiver receives signals from the remote control and forwards them to the keyless vehicle module (KVM).
The remote keyless entry (RKE) receiver has a logic which enables it to check that a correct message is received. All communication is decrypted in the keyless vehicle module (KVM).
The remote keyless entry (RKE) receiver has two different modes:
- normal mode
- passive mode.
In normal mode, the receiver waits for a signal from the remote control when a button is pressed.
If the keyless vehicle module (KVM) receives an indication from the door handle that someone is trying to open the vehicle using keyless entry, the keyless vehicle module (KVM) transmits a signal to the receiver to switch to passive mode for a pre-determined period of time. After this time, the receiver reverts to normal mode. The difference between these two modes is the way in which the receiver communicates with the key.
When a key has been approved and is used to start the vehicle, or if there is a key in the ignition switch, the keyless vehicle module (KVM) ignores all messages from the remote keyless entry (RKE) receiver. This prevents the central locking system from unlocking if a button on the remote control is unintentionally pressed in.
The remote keyless entry (RKE) receiver is powered by the central electronic module (CEM) and grounded in the A-post.
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).