Body Electrical System > Smart key System > Description and Operation

Description

The system is a system that allows the user to access and operate a vehicle in a very convenient way. To access the vehicle no traditional key or remote control unit is needed.The user carries a Smart K FOB which itself does not require any conscious actions by the user (e.g. operate a button). The SMART KEY system is triggered by pressing a push button in the door handle. After being triggered the vehicle sends out a request in a limited range. If the SMART KEY FOB receives this request, it automatically sends a response to the vehicle. Then the system decides whether to perform a particular action (unlocking, locking...) or remain inactive.In a similar manner the vehicle's Mechatronic Steering Lock (MSL) is released. Again, a communication between the vehicle and the SMART KEY FOB is needed before any actions will be performed.

Scope Of Smart Key System

The System offers the following features :

•	passive access via door driver side and passenger side

•	passive locking via door driver side and passenger side

•	passive start

•	passive access trunk/tailgate via the trunk lid switch at the trunk

•	passive locking via tailgate

•	max. 2 fobs can be handled by the system

•	immobilizer backup antenna driver integrated into MSL for TP authentication (i.e. limp home mode)

•	communication with engine management system via EMSCOM

•	communication with MSL via MSLCOM

•	communication with SRX via SRXCOM

•	LF-RF communication (based on Siemens' SMART KEY system)

•	block of the steering column by the MSL device.

Operation

Passive Functions

The system allows the user to access the vehicle without having to perform any actions (button pushes) with the SMART KEY FOB. It is sufficient that a valid SMART KEY FOB is located within a defined and limited range with respect to the vehicle. So the system is capable of detecting and authenticating a SMART KEY FOB in the ranges as specified below.

Passive Access (Passive Entry)

If user press Front left side push button, when all doors locked (that includes tail gate if tail lock bit set) indicates the operator's intent to access the vehicle and thus triggers the system for unlock and two steps timer is started. If user press Front left side push button one more time while the two steps timer is still running, then system is triggers for a second unlock.Pressing front right side push button in the door handle when all doors are locked indicates the operator's intent to access the vehicle and thus triggers the system for an unlock.Subsequently, the SMK ECU sends a LF-challenge to the SMART KEY FOB via the corresponding exterior antenna. The SMART KEY FOB answers with a RF-response. If the received response matches the expected answer, the SMK ECU issues an "unlock" message to the BCM module via the CAN/LIN network.

Passive Locking (Exit)

Pressing one of the push buttons in the door handles when (at least one door unlocked and two steps timer not running) or (two steps timer running and one of the push button except Front Left side is triggered) indicates the operator's intent to lock the vehicle and thus triggers the system for a lock.

Passive Access Trunk

Pressing the Trunk Lid Switch when trunk is closed indicates the operator's intent to open the trunk and thus triggers the system. Subsequently, the SMK ECU sends a LF-challenge to the SMART KEY FOB via the exterior bumper antenna. The SMART KEY FOB answers with a RF-response. If the received response matches the expected answer, the SMK ECU sends a "trunk open" message via the CAN/LIN network.Special case: If the car is locked, but the ATWS is not armed, LF strategy shall search for FOB at the bumper area excluding trunk and interior area.

Passive Open Tailgate

Pressing the Tailgate Lid Switch when tail gate is closed indicates the operator's intent to open the tailgate and thus triggers the system. Subsequently, the SMK ECU sends a LF-challenge to the SMART KEY FOB via the exterior bumper antenna. The SMART KEY FOB answers with a RF-response. If the received response matches the expected answer, the SMK ECU sends a "tailgate open" message via the CAN/LIN network.

Smart Key Reminder 1

Preconditions : All terminals OFF and at least one door open and no Key-In and locking status is not locked (to be checked by SMK ECU periodically every 100ms, as long as CAN/LIN active)

User action : At least 1 door knob status changed from unlock to lock.

Vehicle action : locking status changes from unlock to lock.

SMK ECU actions : the SMK ECU performs a search for the fobs in the interior of the vehicle; the same LF-strategy has to be used as it is defined for the ID out warning (registering only, no authentication).If no fob has been found, no action is required.If any fob has been found, the SMK ECU unlocks the vehicle by sending a CAN/LIN passive unlock message with the fob number.

Smart Key Reminder 2

Preconditions : All terminals OFF and any door (including tail gate) open and no Key-In and locking status is not locked (to be checked by SMK ECU periodically every 100ms, as long as CAN/LIN active)

User action : All doors and tail gate closed.

Vehicle action : Closing last door or tail gate with knobs state locked, or with a locking in progress

SMK ECU actions : if within 500ms following the closing, all doors are locked then SMK ECU performs a search for the fobs in the interior of the vehicle; the same LF-strategy has to be used as it is defined for the ID out warning (registering only, no authentication).If no fob has been found, no action is required.If any fob has been found, the SMK ECU unlocks the vehicle and activates ext. buzzer warning.

Smart Key Door Lock Warning

Door Lock Warning 1

If (TAIL BIT is not set) AND (TAIL BIT is set & TAIL LOCK BIT is not set), this warning can be triggered when below conditions are fulfilled.

Preconditions : (All doors are closed) and (ACC ON or IGN1 ON) and no Key in User action : user presses the door handle Push button.SMK ECU actions: the SMK ECU performs a search for the fobs outside of the vehicle; the same LF-strategy has to be used as it is defined for Passive Access Door Unlock.

If TAIL LOCK BIT is set, this warning can be triggered when below conditions are fulfilled.Preconditions : (All doors are closed) AND (Tailgate is closed) and (ACC ON or IGN1 ON) and no Key in

User action : user presses the door handle Push button OR tailgate Push button.SMK ECU actions : the SMK ECU performs a search for the fobs outside of the vehicle; the same LF-strategy has to be used as it is defined for Passive Access Door Unlock.

If no fob has been found, no action is required.If any fob has been found, the SMK ECU activates the external buzzer.If the preconditions are no longer valid during buzzer active time (3 seconds), the SMK ECU stops the buzzer immediately.

Door Lock Warning 2

Preconditions : Same as passive locking precondition but with at least one door openUser action : user presses the door handle Push button or (tailgate push button if TAIL LOCK BIT set)SMK ECU actions : the SMK ECU performs a search for the fobs outside of the vehicle; the same LF-strategy has to be used as it is defined for Passive Access Door Unlock.

Door Lock Warning 3

Preconditions : Same as passive locking preconditionUser action : user presses the door handle Push button OR Tailgate push button if TAIL LOCK BIT setSMK ECU actions : If ATWS is DISARM, SMK ECU performs a search for the fobs inside of the vehicle (use "Door Lock Warning 3" scenario)If any fob has been found, SMK ECU activates the external buzzer.If the activity timer elapsed or ACC ON or IGN1 ON or NOT (All door closed) or Key IN, the SMK ECU stops the buzzer immediately. After searching of inside fob, SMK ECU also performs a search for fobs outside of the vehicle.

Smart Key Lamp Warning

Preconditions : (ACC ON or IGN1 ON) and no Key-In and CAN-Bit "3km" not setUser action : noneSMART KEY actions : as long as the preconditions are valid, the SMK ECU performs a periodical search for the fobs in the interior of the vehicle; the same LF-strategy has to be used as it is defined for the ID out warning (registering only, no authentication); periodical means, the search has to be started all 3 seconds.If no fob has been found, the SMK ECU starts Key out indicator lamp activation as all preconditions are valid and will perform an other search 3 seconds later.If any fob has been found, the SMK ECU stops the Key out indicator lamp and will (if one door is open) perform an other search 3 seconds later; if no door is open then it's only at the next opening of one door if the condition are still valid that the search will be resumed.

Failsafe Functions (Backup For Limp Home)

In case of a discharged battery of the SMART KEY FOB or disturbed transmission the following functions are available :

•	Unlocking / locking of doors or trunk (or tailgate depending of the vehicle configuration) : use of mechanical key.

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Release of the steering column : The SMART KEY FOB has to contain the transponder functionality. To release the steering column and to start the engine the driver has to insert the SMART KEY FOB into the MSL and then the driver has to push the MSL Knob. When the SMK ECU detects the active MSL Knob Push Switch and the active Key-In contact, it sends a command to the MSL to start a transponder authentication. The MSL communicates via the transponder antenna with the transponder. When the transponder code is correct the MSL releases the ignition switch.

•	Engine Start : To start the engine the driver turns the rotary knob to 'IGN' (ignition) position. The EMS sends an immobilizer challenge to the SMK ECU which responds with a 'go' or a 'no go'. The EMS gives the definite release to start the engine.

User Information Functions

ID Out Warning

If at least one door open and the last door will be closed and the terminals are not 'Off', the SMK ECU searches for a SMART KEY FOB in the interior. If no valid SMART KEY FOB is found the SMK ECU generates a corresponding warning and sends by CAN/LIN request for internal buzzer activation (exterior buzzer warning and internal buzzer warning). If a door will be opened and closed again during terminals on and a valid fob will be found then within the vehicle, the SMK ECU re-enables the authentication and stops the warning.

If there is a LF error (LF overheating or LF antenna failure), the system will have the same behavior as it is with no fob found.

ID Not Found For Passive Start

For the passive start functionality (not for the limp home start), an ID has to be detected in the interior of the vehicle. If no valid SMART KEY FOB is found, the SMK ECU starts an immobilizer interrogation in the MSL; if also the immobilizer interrogation fails, the SMK ECU activates the immo lamp.

MSL Not Blocked Warning

If no fob is inserted and ACC off and IGN1 off and the MSL is not blocked (MSL blocked switch in MSL) or at the time of the MSL not block warning strategy the status is unknown while the last command was a block command and the driver door is open, the SMK ECU generates a corresponding warning via the interior buzzer.

MSL not blocked warning will appear as long as the driver door is open and the terminals are off only if a MSL block command has been issued but without result or without known result (MSL not blocked).

Immobilizer Lamp

Cases like releasing the MSL Knob in OFF position will switch off the immobilizer lamp. Removing the PIF from the MSL and reinserting the PIF and pushing the MSL Knob will switch the lamp on again.

FOB Battery Low Voltage Detection

To detect, if the voltage of the fob battery is no longer sufficient, a certain battery voltage measurement and low voltage detection strategy is implemented in the fob. The measurement of the battery voltage will be done, if a button is pressed or if a LF measurement command is received. To ensure a valid result, it is not sufficient to do only a measurement, if a button is pressed (e.g. if the driver only uses the passive mode and never presses a button). Therefore the SMK ECU sends a measurement command to the fob. This command is sent once during an IGN1 ON cycle, if the speed exceeds 40 km/h for the first time.If the PIF has detected a low battery voltage, the LED will not be switched on at button press.