Design

Design

General
The security system in the vehicle is a distributed system which is monitored by the central electronic module (CEM). A number of other units and components are involved for the various functions.

Central electronic module (CEM)




The central electronic module (CEM) (4/56) is the master unit for the immobilizer. The central electronic module (CEM), steering column lock module (SCL), ignition antenna unit (IAU) and the engine control module (ECM) are linked by codes. The central electronic module (CEM) is also programmed with codes for each ignition key that belongs to the vehicle.
If the vehicle has an Alcolock (option) installed, the code in the handset unit must also be programmed into the Central electronic module (CEM) to work. The signal from the Alcolock handset is received by the Remote Receiver Module (RRX), which forwards the signal to the Central electronic module (CEM).
The central electronic module (CEM) transits commands and signals to the other control modules included in the system. The identity of the remote key is checked by the central electronic module (CEM) via the ignition antenna unit (IAU) or by the keyless vehicle module (KVM) via the antennas (only vehicles with the keyless locking system). Which control module that validates the remote key depends on whether the vehicle is being started passively or not. There is a communication circuit in the remote key, known as a transponder. The transponder has a unique identification code that must be learned by the central electronic module (CEM) before the remote key can be used to start the vehicle. This learning process takes place during installation at the factory. New remote keys can be added afterwards.
If there is a keyless vehicle module (KVM) installed in the vehicle, the central electronic module (CEM) requests that it checks the identity of the remote key when:
- the starter button is pressed
- the clutch pedal is depressed (MAN)
- the brake pedal is depressed (AUT).
The central electronic module (CEM) controls the relay for the fuel pump (FP). When the identity of the remote key and all included components have been checked, the central electronic module (CEM) activates the fuel pump (FP) after a command from the engine control module (ECM).
For further information about the central electronic module (CEM), see Design and Function, central electronic module (CEM).

Keyless vehicle module (KVM) (only vehicles with the keyless locking system)




The keyless vehicle module (KVM) controls the keyless functions in the vehicle. The keyless vehicle module (KVM) works together with the central electronic module (CEM) when checking the key identity.
For more information see Function/System for Immobilizer and Design and function, Keyless vehicle module (KVM).

Ignition antenna unit (IAU)




Ignition antenna unit (IAU) is installed in the instrument panel beside the steering wheel.
The Ignition antenna unit (IAU) has an internal antenna that can be activated on command from the Central electronic module (CEM). The antenna is used for checking the key identity when the remote key is inserted in the ignition. The antenna is activated by the Central electronic module (CEM) when start button (IAU) is pushed.
The remote key does not need to be inserted in the ignition if there is a keyless vehicle module (KVM) in the vehicle. The identity of the remote key is then checked via the antennas in the passenger compartment instead. These antennas are connected to the keyless vehicle module (KVM) when start button (IAU) is pushed.
The Ignition antenna unit (IAU) is powered by the central electronic module (CEM) and grounded in the body.

Start button




start button (IAU) has two switches, switch 1 and switch 2. Switch 1 is directly connected to Central electronic module (CEM), Keyless vehicle module (KVM), and Engine control module (ECM). Switch 2 is only directly connected to Central electronic module (CEM).
Both switches should close when start button (IAU) is pushed. It is enough for one switch in start button (IAU) to be closed for the vehicle to start. If the signals from the switches show different status on start button (IAU) a fault code is set in Central electronic module (CEM), and the function for autostart is lost.

Note! If only one of the switches for the start button is OK, the vehicle can only be turned off if it is stationary.

Remote key




The remote key has a different number of buttons depending on the configuration of the vehicle. The information button is only found on vehicles with the keyless function installed. The remote keys differ in design depending on whether it contains the function for keyless entry of not. All remote keys contain a key blade. The key blade is normally retracted inside the remote key. The blade is used as a standby option to open the vehicle should there be a fault in the electric central locking system.

The buttons on the remote key are:
- Button to lock the vehicle
- Button to unlock the vehicle
- A button to unlock the trunk lid/tailgate
- A button to activate the vehicle lighting for 30 seconds
- Button to activate the vehicle's horn (only vehicles with alarms)
- Button to activate the heartbeat sensor and status check (only vehicles with keyless function installed)
The remote key, regarding internal design, consists of three sections:
- Transponder
- Circuit for remote control
- Circuit for keyless functionality.
The transponder is used so that the immobilizer system can identify the remote key when it is inserted in the ignition. The transponder contains a unique code. The central electronic module (CEM) must be programmed with the transponder code before the vehicle can be started.
The circuit for remote control is used to lock and unlock the central locking and to activate the above functions. The circuits in the remote key that control the functionality are coded. These codes must be programmed into the Central electronic module (CEM) (vehicles without keyless function) or the Keyless vehicle module (KVM) (vehicles with keyless function) for communication to work.
The circuit for keyless functionality is used for:
- Unlocking
- Locking
- Passive starting
The circuits in the remote key which control the function for the keyless entry system are coded. The keyless vehicle module (KVM) must learn these codes for communication to function.
The remote key is powered by an internal button battery. The battery is used each time a remote key needs to communicate with the system via the remote control or keyless function. The battery is not used during communication with the key transponder when the remote key is in the ignition. The battery must be replaced at regular intervals depending on how often the remote key is used. The remote key contains an internal voltmeter that measures the voltage of the internal battery. If the battery's voltage becomes too low, the information about this is transmitted in the messages to the Remote Receiver Module (RRX). The Central electronic module (CEM) or Keyless vehicle module (KVM) (only vehicles with keyless function) receives the information and transmits a message via the CAN network to the Driver information module (DIM), which shows a message that the voltage is too low. Reduced remote key range is also an indication that the battery charge is low.

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

1. Only applies to vehicles with the system for keyless function installed: If a button on the remote key is pressed when identifying the remote key, identification will fail. This is because the remote key cannot transmit and receive data at the same time (when a button is pressed in on the remote key it is busy transmitting "normal" remote control commands). This fault can occur if the remote key is in a pocket or a bag and a button is pressed accidentally.
2. Due to increased ambient radiation, for example, from TV/radio transmitters and mobile phones, the signal from the remote key can, in some cases, be interrupted. Examples of sources of interference can be: wireless headsets, remote controls for other vehicles and manufacturers, remote controlled garage door openers, meters with remote reading and wireless weather stations. Radio waves from all these sources can create an area where all wireless communication, in principle, is impossible. In many cases this occurs, in certain locations, where different outside signals make transmission and reception conditions unfavorable. This affects not only remote control functions but all types of wireless communication.
For further information about the keyless function, see Design and function, Keyless vehicle module (KVM).

Alcolock (option)
See Design and Function, Alcohol Analyzing Start Inhibitor.

Steering column lock module (SCL)




Steering column lock module (SCL) (4/102) checks the function of the steering wheel lock. The control module is installed the underside of the steering column inside the passenger compartment. Steering column lock module (SCL) is connected serially to Central electronic module (CEM) for communication and directly connected to Central electronic module (CEM) for voltage feed. Steering column lock module (SCL) is only supplied with voltage when locking or unlocking.
Central electronic module (CEM) sends out commands to Steering column lock module (SCL) when locking and unlocking is to take place. Communication between Steering column lock module (SCL) and Central electronic module (CEM) is encrypted. For Steering column lock module (SCL) to function in the vehicle it must be loaded with codes for the immobilizer function. This takes place when downloading software.

The steering column lock module (SCL) consists of:
- an electric motor
- a spring bolt
- a communication circuit
- a switch.
The steering column lock module (SCL) locks the steering wheel using the spring bolt. The spring bolt is moved back and forth by the electrical motor. The position of the spring bolt is indicated by the contact breaker in the steering column lock. The steering column lock module (SCL) transmits information at regular intervals about the position of the spring bolt to the central electronic module (CEM). A diagnostic trouble code (DTC) is stored in the central electronic module (CEM) if the spring bolt cannot reach its unlocked position or its position cannot be determined. A message will also be shown in the display on the driver information module (DIM).

Hint: If the steering wheel is loaded when trying to unlock the steering column lock, the motor for the lock may be unable to unlock it (too much pressure on the spring bolt). An error message will be shown in the display on the driver information module (DIM) if this is the case. If this should happen, move the steering wheel slightly to reduce the pressure on the spring bolt, before a new start attempt.

The steering column lock module (SCL) is powered by the central electronic module (CEM) and grounded in the body.
For more information on steering column lock, see: Function Function

Engine control module (ECM)




The engine control module (ECM) (4/46) checks the relay for the starter motor and the ignition system. The logic for the start inhibition system is also in the engine control module (ECM). The engine control module (ECM) also transmits a command to the central electronic module (CEM) indicating when the fuel pump (FP) can be activated. The functions are activated after:
1. the remote key is approved
2. the steering column lock is unlocked
3. the communication check has been run with the central electronic module (CEM) and the brake control module (BCM).
The engine control module (ECM) must be programmed with codes before it can work in the immobilizer system. This takes place for the first time during assembly in the factory, and subsequently takes place in the event the control module is replaced (when downloading software)
As a further safety precaution, the engine control module (ECM) reads off the serial number from the brake control module (BCM). These numbers are compared with the number programmed into the engine control module (ECM). The engine will not start if the numbers do not correspond. This means that these numbers must be programmed into the engine control module (ECM) if it or the brake control module (BCM) has been replaced. This takes place automatically when downloading software.
The engine control module (ECM) transmits the status of the engine (whether it is running or not) on the controller area network (CAN). The central electronic module (CEM) and the Driver information module (DIM) use this signal together with the signals from the brake control module (BCM) and transmission control module (TCM) to determine whether the steering column lock can be locked or not.
For more information regarding the engine management system, see Design and Function, Engine Control Module (ECM).

Brake control module (BCM)




The brake control module (BCM) (4/16) transmits signals on the controller area network (CAN) about the vehicle speed. The central electronic module (CEM) uses this signal to determine whether the vehicle is moving. The central electronic module (CEM) uses these signals from the brake control module (BCM) to determine whether the steering column lock can be locked or not.
When deactivating the immobilizer system, the communication between the engine control module (ECM) and brake control module (BCM) is checked. During this check, the engine control module (ECM) reads off the serial number from the brake control module (BCM) and compares this with a number it has programmed. The engine will not start if the numbers do not correspond.
For further information, see Design and Function, Brake control module (BCM).

Transmission control module (TCM)




Transmission control module (TCM) (4/28) transmits signals on the CAN network with the position of the gear selector. The central electronic module (CEM) uses this signal to determine if the gear selector is in P or N.
The vehicle can only be started if the gear selector is in position P or N.
For more information, see Design and Function - Transmission control module (TCM).

Driver information module (DIM)

Location Of Components:

The driver information module (DIM) (5/1) receives information from the central electronic module (CEM) about which message is to appear in the display. A message will be displayed if there is a fault in any of the checks run by the system.
For further information, see Design and Function, driver information module (DIM).