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Home >> Volvo >> 2007 >> S80 AWD V8-4.4L VIN 85 B8444S >> Repair and Diagnosis >> Accessories and Optional Equipment >> Antitheft and Alarm Systems >> Description and Operation >> Immobilizer/Start Inhibition >> Function

Function






Function

Start inhibition
The start inhibition system is a comprehensive function of the security system. The start inhibition system compiles a number of parameters from the various security functions in the vehicle and then determines whether a start attempt is permitted. The checks that are run are:
- Checking depressed pedals.
- The clutch pedal must be depressed on vehicles with manual transmissions.
- The brake pedal must be depressed on vehicles with automatic transmissions.
- Checking the position of the gear selector. On cars with automatic transmissions, the gear selector must be in position P (park) or N (neutral).
- Checking the immobilizer. All checks run by the immobilizer must be OK.
- Checking the steering column lock. The steering column lock must be unlocked.
The function for start inhibition is checked by the engine control module (ECM). This function is based entirely on signals on the controller area network (CAN). For further information about the start process, see Design and Function, engine control module (ECM).

Immobilizer system
The immobilizer system prevents the vehicle from being used if a non Volvo original key for that vehicle is used to start the vehicle. The identity of the remote key is checked electronically when to ensure that the correct remote key is inserted in the Start control module (SCU). On cars with the keyless system it is checked by the keyless vehicle module (KVM). If the remote key is not approved, the steering column lock will not be unlocked and the engine will not start. The customer will not notice the function of the system as long as a valid remote key is used and no fault occurs.

Deactivation and start (only cars without the keyless locking system)




To deactivate the immobilizer system, the remote key must be inserted in the Start control module (SCU) (3/132). When the remote key is inserted in the Start control module (SCU), the Central electronic module (CEM) (4/56) transmits the command to the Start control module (SCU) that the remote key identity must be checked. The Start control module (SCU) activates the antenna and reads off the identity code from the remote key's transponder. This code is transmitted to the Central electronic module (CEM) and compared with the codes that are programmed in the Central electronic module (CEM). If the read off code from the remote key is in the Central electronic module (CEM), the key is approved.
Central electronic module (CEM) will then activate voltage supply to the fuel pump module (PEM).
The central electronic module (CEM), after approval of the remote key, checks the signals on the CAN network regarding the vehicle speed and engine status. If the vehicle is stationary and the engine is not idling, the Central electronic module (CEM) transmits a signal to the Driver information module (DIM) (5/1) indicating that the power supply to the Steering column lock module (SCL) (4/102) must be activated. The Driver information module (DIM) also checks the signals for the engine status and the vehicle's speed on the CAN network. If the Driver information module (DIM) concludes that the engine is not running and the vehicle is stationary, the Driver information module (DIM) transmits a signal that activates a relay in the Central electronic module (CEM). The power is forwarded to the Steering column lock module (SCL) via this relay. The Driver information module (DIM) also transmits an acknowledgement via CAN to the Central electronic module (CEM) that the power supply has been activated. If the starter button has been pushed and the remote key is approved, the central electronic module (CEM) transmits a command to the steering column lock module (SCL) to unlock the steering column lock. The vehicle cannot be started before the spring bolt in the steering column lock module (SCL) is in the unlocked position. The position of the spring bolt is indicated by a contact breaker in the Steering column lock module (SCL) and is connected to the Central electronic module (CEM). A communication check is carried out continuously, whilst driving, between the Central electronic module (CEM) and the Driver information module (DIM) to ensure that the Steering column lock is not activated by mistake while driving. If the central electronic module (CEM) detects that power supply to the steering column lock module (SCL) is too high for any reason while driving, a warning message is displayed in the driver information module (DIM).
When the ignition is switched on or a start attempt is made (by depressing a pedal and pushing the starter button), the communication between the central electronic module (CEM) and engine control module (ECM) is checked. This is to ensure that the correct codes are programmed into both control modules. The engine control module (ECM) also checks the identity of the brake control module (BCM) (4/16) by reading off its serial number. This number is compared with the number programmed into the engine control module (ECM). If these checks are completed satisfactorily, the engine control module (ECM) activates the ignition system. The engine control module (ECM) also transmits a command to the central electronic module (CEM) to allow the fuel pump (FP) to continue to run. If a fault should occur or a check is not approved, the engine control module (ECM) instructs the central electronic module (CEM) to deactivate the fuel pump (FP). The engine control module (ECM) also checks the other parameters covered by the start inhibition function. If all conditions are met, the engine control module (ECM) activates the relay for the starter motor. The engine can then be started.
If any of the above steps should fail, the engine will not start and a message will be displayed in the driver information module (DIM).
The immobilizer system has built-in diagnostic test modes (DTM) to ensure that the engine can be restarted after unintentional stops.

Passive deactivation and start (only cars with the keyless locking system)




To carry out a start of a keyless vehicle, a pedal must be depressed (clutch (MAN) or brake (AUT)) and the starter button pushed. When the starter button is pushed, an input on the keyless vehicle module (KVM) (4/93) is grounded, which searches for a remote key with passive function in the vehicle. Ground connection from the starter button also goes to the Central electronic module (CEM) (4/56), which, at the same time, transmits an encrypted request to the Keyless vehicle module (KVM). This request is responded to only if an approved passive remote key has been registered. If a remote key is found, the keyless vehicle module (KVM) checks that it is approved. If this is the case, the keyless vehicle module (KVM) transmits a response to the central electronic module (CEM) indicating that the remote key is approved.
If a passive remote key is not registered, the keyless vehicle module (KVM) will transmit a negative response to the central electronic module (CEM). The central electronic module (CEM) will then transmit a request to the start control module (SCU) (3/132) instead to search for a transponder. The central electronic module (CEM) will approve the remote key if a transponder is found.
If a start attempt is made, either on a non keyless or keyless vehicle, the Central electronic module (CEM) checks the signals on CAN regarding the speed and status of the engine. If the vehicle is stationary and the engine is not idling, the Central electronic module (CEM) transmits a signal to the Driver information module (DIM) (5/1) indicating that the power supply to the Steering column lock module (SCL) (4/102) must be activated. The Driver information module (DIM) also checks the signals for the engine status and the vehicle's speed on the CAN network. If the Driver information module (DIM) concludes that the engine is not running and the vehicle is stationary, the Driver information module (DIM) transmits a signal that activates a relay in the Central electronic module (CEM). The power is forwarded to the Steering column lock module (SCL) via this relay. The Driver information module (DIM) also transmits an acknowledgement via CAN to the Central electronic module (CEM) that the power supply has been activated. If the starter button has been pushed and the remote key is approved, the central electronic module (CEM) transmits a command to the steering column lock module (SCL) to unlock the steering column lock. The vehicle cannot be started before the spring bolt in the steering column lock module (SCL) is in the unlocked position. The position of the spring bolt is indicated by a contact breaker in the Steering column lock module (SCL) and is connected to the Central electronic module (CEM). A communication check is carried out continuously, whilst driving, between the Central electronic module (CEM) and the Driver information module (DIM) to ensure that the Steering column lock is not activated by mistake while driving. If the central electronic module (CEM) detects that power supply to the steering column lock module (SCL) is too high for any reason while driving, a warning message is displayed in the driver information module (DIM).
When the ignition is switched on or a start attempt is made (by depressing a pedal and pushing the starter button), the communication between the central electronic module (CEM) and engine control module (ECM) is checked. This is to ensure that the correct codes are programmed into both control modules. The engine control module (ECM) also checks the identity of the brake control module (BCM) (4/16) by reading off its serial number. This number is compared with the number programmed into the engine control module (ECM). If these checks are completed satisfactorily, the engine control module (ECM) activates the ignition system. The engine control module (ECM) also transmits a command to the central electronic module (CEM) to allow the fuel pump (FP) to continue to run. If a fault should occur or a check is not approved, the engine control module (ECM) instructs the central electronic module (CEM) to deactivate the fuel pump (FP). The engine control module (ECM) also checks the other parameters covered by the start inhibition function. If all conditions are met, the engine control module (ECM) activates the relay for the starter motor. The engine can then be started.
If any of the above steps should fail, the engine will not start and a message will be displayed in the driver information module (DIM).
The immobilizer system has built-in diagnostic test modes (DTM) to ensure that the engine can be restarted after unintentional stops.

Activation
The immobilizer system is activated when the ignition is switched off. The engine cannot be started when the system is activated. The engine control module (ECM) then deactivates the ignition system and the relay for the starter motor. The central electronic module (CEM) deactivates the fuel pump (FP) at the same time. If the driver's door is opened, the Central electronic module (CEM) checks the signals on CAN regarding the engine status and the vehicle speed. If the vehicle is stationary and the engine is off a command is transmitted to the Driver information module (DIM), to activate the power supply to the Steering column lock module (SCL). The Driver information module (DIM) also checks the signals for the engine status and the vehicle's speed on the CAN network. If the Driver information module (DIM) concludes that the engine is not running and the vehicle is stationary, the Driver information module (DIM) transmits a signal that activates a relay in the Central electronic module (CEM). The power is forwarded to the Steering column lock module (SCL) via this relay. The Driver information module (DIM) also transmits an acknowledgement via CAN to the Central electronic module (CEM) that the power supply has been activated. The central electronic module (CEM) then transmits a command to the steering column lock module (SCL) to lock the steering column lock.

Remote key lock
Included in the security system is the function for locking the remote key in the Start control module (SCU). This function means that the remote key cannot be removed if the gear selector is not in the park (P) position.(only cars with automatic transmissions).
For cars without automatic transmissions, the vehicle must be stationary and engine off in order for the key to be removed.
This function is checked by the central electronic module (CEM). The Start control module (SCU) contains a contact breaker that closes when the remote key is pressed to the limit position in the Start control module (SCU). The contact breaker indicates to the Start control module (SCU) that the motor for insertion and ejection of the remote key must be activated to draw in or eject the remote key. The Central electronic module (CEM) continually checks if remote key ejection is permitted by checking the signals for:
- engine status from the Engine control module (ECM)
- gear selector position from the Transmission control module (TCM)
- vehicle speed from the Brake control module (BCM).
A message is transmitted at regular intervals to the Start control module (SCU) about whether the remote key can be removed or not. If the remote key is inserted and ejection is permitted according to the Central electronic module (CEM) , the Start control module (SCU) activates the motor for insertion and ejection. If the gear selector is not in position P, a message is displayed in the Driver information module (DIM), with a request to shift the gear selector to the P position. The remote key will not be ejected.

Key warning
The key warning function is part of the security system. For vehicles without the keyless function there is only key warning on vehicles on the USA/CDN market. The components in the function are the central electronic module (CEM) and the driver information module (DIM). The warning activates when the driver's door is opened when the remote key is in the Start control module (SCU). A contact in the lock unit of the driver's door indicates that the driver's door was opened.
If the system for keyless functions is installed, the antennas inside the vehicle are activated each time the driver's door is opened. The system then scans for the key which was used to start the vehicle. A warning message is displayed in the driver information module (DIM) if this key is not found. The engine will continue running, but the engine is switched off it will not start again if there is not another valid remote key inside the vehicle.
For vehicles with the keyless function the signal is also activated and a message is displayed in the Driver information module (DIM) if the vehicle is in any other ignition position than "ignition off" when the driver's door is opened and the engine is switched off.

Steering column lock
The central electronic module (CEM), Driver information module (DIM) and steering column lock module (SCL) are part of the steering column lock function. The power supply to the Steering column lock module (SCL) is controlled by the Driver information module (DIM) via a relay in the Central electronic module (CEM). The steering column lock module (SCL) also receives commands from the central electronic module (CEM) to lock or unlock the steering column lock. The steering column lock only permits a function to be carried out when the vehicle is not in motion and the engine is off.
Whilst the vehicle is being driven, communication checks are carried out between the Driver information module (DIM) and the Central electronic module (CEM) to ensure that the Steering column lock is not activated by mistake. At the same time, the central electronic module (CEM) monitors the communication cable to the steering column lock module (SCL). If the central electronic module (CEM) detects that the steering column lock module (SCL) starts communicating when it should not be powered, the central electronic module (CEM) will display an warning message in the driver information module (DIM) and will attempt to disengage the steering column lock.
Unlocking
When the central electronic module (CEM) receives a signal from the starter button (applies to vehicles with keyless function) or when the remote key is inserted in to the start control module (SCU) the key identity is checked, either via the keyless system or via the start control module (SCU). After approved validation of the remote key the central electronic module (CEM) transmits a command to the Driver information module (DIM) to power the Steering column lock module (SCL). The Driver information module (DIM) checks, using the signals from the Engine control module (ECM) and the Brake control module (BCM) that the engine is not running and the vehicle is stationary. If the conditions are met the Driver information module (DIM) activates power to the Steering column lock module (SCL). The Central electronic module (CEM) carries out the same checks as the Driver information module (DIM). If the Central electronic module (CEM) also considers the conditions to have been met the Central electronic module (CEM) gives an unlocking command to the Steering column lock module (SCL). The steering column lock module (SCL) then attempts to unlock the steering column lock. If everything is OK, the steering column lock module (SCL) transmits two signals back to the central electronic module (CEM).One signal indicates that the steering column lock module (SCL) has not detected any internal faults and is functioning as intended. The other signal indicates that the spring bolt has moved to the unlocked position. The central electronic module (CEM) will then store an internal value for successful unlocking and then continues with the checks for the immobilizer system.
If the steering column lock does not unlock the first time, the steering column lock module (SCL) will make a further two unlocking attempts. The power supply to the Steering column lock module (SCL) is switched off between each attempt. If these also fail, the steering column lock module (SCL) will transmit a message about the fault to the central electronic module (CEM). The central electronic module (CEM) will then store a diagnostic trouble code (DTC) and the checks for the immobilizer system will be cancelled. It will not then be possible to start the engine.
Locking
The following applies to vehicles without the keyless locking system:
The Central electronic module (CEM) receives a ground connection from the contact breaker in the Start control module (SCU) that indicates that the remote key has been pushed to its limit position when it is to be removed from the Start control module (SCU). When the signal is received, the Central electronic module (CEM) checks the signals on CAN that:
- the engine is switched off, from the Engine control module (ECM)
- the vehicle is stationary, from the Brake control module (BCM).
If the engine has been switched off and the vehicle is stationary, the Central electronic module (CEM) transmits a message to the Driver information module (DIM), to activate the power supply to the Steering column lock module (SCL). The Driver information module (DIM) then checks the signals on CAN, that the engine is switched off and that the vehicle is stationary. If this is the case the Driver information module (DIM) activates the power supply to the Steering column lock module (SCL), via a relay in the Central electronic module (CEM), and transmits an acknowledgement to the Central electronic module (CEM) via CAN stating that power is on. The Central electronic module (CEM) will then transmit a message to the Steering column lock module (SCL). The Steering column lock module (SCL) transmits a message back to the Central electronic module (CEM) stating whether locking was successful or not. The central electronic module (CEM) will store a diagnostic trouble code (DTC) if locking has failed after 3 attempts.
Locking
The following applies to vehicles with the keyless locking system:
After the ignition has been switched off and the driver's door opened, the Central electronic module (CEM) checks the signals on CAN that:
- the engine is switched off, from the Engine control module (ECM)
- the vehicle is stationary, from the Brake control module (BCM).
If the engine has been switched off and the vehicle is stationary, the Central electronic module (CEM) transmits a message to the Driver information module (DIM), to activate the power supply to the Steering column lock module (SCL). The Driver information module (DIM) then checks the signals on CAN, that the engine is switched off and that the vehicle is stationary. If this is the case the Driver information module (DIM) activates the power supply to the Steering column lock module (SCL), via a relay in the Central electronic module (CEM), and transmits an acknowledgement to the Central electronic module (CEM) via CAN stating that power is on. The Central electronic module (CEM) will then transmit a message to the Steering column lock module (SCL). The Steering column lock module (SCL) transmits a message back to the Central electronic module (CEM) stating whether locking was successful or not. The central electronic module (CEM) will store a diagnostic trouble code (DTC) if locking has failed after 3 attempts.

Note! The steering column lock module (SCL) is power connected to the central electronic module (CEM). However, activation of the power supply is controlled by the Driver information module(DIM). This is so that a control module cannot activate the steering column lock by itself. Both the Central Electronic Module (CEM) and the Driver information module (DIM) listen on the CAN for signals such as motor status (from the Engine Control Module (ECM)) and vehicle speed signals.

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