BMW 7 Series: Functions

Function Overview

Comfort Access is divided into the following functions:

• Passive Entry
• Passive Go
• Passive Exit.

ID transmitters are required for Comfort Access to function.

An ID transmitter comprises, among other things:

• A battery
• Remote control function
• Transponder coil for emergency start function
• Mechanical key
• Receiver unit.

Remote Control Function for Comfort Access

When the unlocking or locking button on the ID transmitter is pressed, it emits an encrypted remote control signal. The antenna in the rear window forwards the remote control signal to the diversity module. The diversity-module remote control receiver demodulates, processes and then sends the signal to the Car Access System on the LIN bus.

If the vehicle is in sleep mode, the remote control receiver wakes the Car Access System to reduced consumption mode via the LIN bus. The Car Access System thus receives the request that was sent using the ID transmitter. The ID transmitter is checked by the remote control receiver at this stage. If the result of the check is positive, the remote control receiver forwards the request via the LIN bus. If the request is authenticated, the Car Access System wakes the vehicle and initiates the unlocking or locking of the vehicle. To do so, the Car Access System issues the release signal for the junction box electronics to actuate the central-locking drive.

The ID transmitter can also be used to open the trunk separately. For this, only the button with the open trunk symbol need be pressed.

The Car Access System is responsible for communication via the LIN bus. The diversity module therefore only forwards the LIN bus signal if prompted to do so by the Car Access System 4. This applies to a vehicle that is not in sleep mode.

Passive Entry

The graphic below shows the functional principle of "Passive Entry".

Fig. 3: Signal Path For Comfort Access In F01/F02 Passive Entry System

COMPONENTS DESCRIPTION CHART

1. Outside door handle electronics module (TAGE)
2. TAGE request to the CAS
3. Prompt about Comfort Access antenna
4. Comfort Access antenna
5. ID transmitter
6. Rear window antenna
7. Remote control receiver in the diversity module
8. Car Access System 4 (CAS 4)

LIN-Bus - Local Interconnect Network bus
f1 - Low frequency in the kHz range
f2 - High frequency in the MHz range
K-CAN2 - Body CAN2
CA/FBD - Comfort Access/remote control services

Passive Entry enables access to the vehicle without the ID transmitter being actively operated.

For example, if the outside door handle is pulled, this triggers a pulse in the sensor. The outside door handle electronics analyze the sensor and inform the Car Access System that vehicle access is requested.

The Car Access System prompts the ID transmitter to identify report to the vehicle. For this, a low-frequency signal is emitted by Comfort Access via the antennas. Transmission is via the 125 kHz antennas.

The 125-kHz signal serves only to wake the ID transmitter. The ID transmitter responds with its transmission frequency. Subsequent communication is now bi-directional, i.e. in two directions. The Car Access System sends or receives all further information via the LIN bus.

The remote control receiver is equipped with both a receiver unit and a transmitter unit. It establishes the connection with the ID transmitter via the rear-window antenna. For that reason, only the high frequency range is now used.

Bi-directional communication has the advantage that data can be requested from or sent to the ID transmitter.

The Car Access System has sole responsibility for this communication.

If the ID transmitter is able to be authenticated, the Car Access System initiate the request, e.g. unlocking the vehicle. The junction box electronics execute the unlocking.

The transmission frequency of the ID transmitter varies for the US is 315MHz.

NOTE: When it is not required, the ID transmitter is in sleep mode. This reduces its energy consumption. For sleep mode to be ended, the ID transmitter requires a wake-up signal. The wake-up signal can be sent by the Car Access System via the Comfort Access antennas. Pressing one of the buttons on the ID transmitter also wakes it.

Passive Entry at the Trunk

An authentication check also takes place before the trunk is opened.

If the outside trunk button in the trunk handle strip is operated, it changes its status. The junction box electronics analyze the status and send it via the K-CAN2.

The Car Access System 4 therefore knows that the outside trunk button has been operated.

The Car Access System initiates the emission of the 125 kHz signal, so that the ID transmitter can report to the vehicle.

At the same time, the Car Access System initiates communication to the ID transmitter.

The Car Access System sends the requests for this via the LIN bus to the remote control receiver. The latter sends the requests from the Car Access System via the rear-window antenna.

If the ID transmitter is recognized as belonging to the vehicle, the Car Access System prompts the junction box electronics to unlock the trunk.

Fig. 4: Principle Of Comfort Access At Trunk

COMPONENTS DESCRIPTION CHART

1. Outside trunk button in the handle strip of the luggage compartment lid
2. Junction box electronics (JB)
3. Car Access System 4 (CAS 4)
4. CAS request to the CA antenna
5. Bumper antenna for Comfort Access
6. ID transmitter
7. Rear window antenna
8. Remote control receiver in the diversity module

LIN-Bus - Local Interconnect Network bus
K-CAN2 - Body CAN2
f1 - Low frequency in the kHz range
f2 - High frequency in the MHz range
CA/FBD - Comfort Access/remote control services

Passive Go

The "Passive Go" function makes it possible to start the vehicle when the ID transmitter is in the passenger compartment.

Issuing Start Enable

Authorization to start the engine is only given when there is an ID transmitter in the vehicle. Once the last door is closed, the Car Access System begins its search for a valid ID transmitter.

The Car Access System 4 requests a signal to be sent out to identify a valid ID transmitter. The interior antennas are used for this.

The ID transmitter responds using a high-frequency range (315 MHz). If the ID transmitter is authenticated, the Car Access System 4 grants permission for the engine to be started.

NOTE: The electronic immobilizer gives its own approval for the engine to be started.

The search for an ID transmitter in the passenger compartment can also be triggered by pressing the START-STOP button. This will take place if the START-STOP button is pressed before the last door is closed, for instance.

Or if the vehicle is stationary too long and therefore loses communication with the ID transmitter. Pressing the START-STOP button triggers the search for the ID transmitter in the vehicle interior.

Passive Exit

The Passive Exit function makes it possible to lock the vehicle without actively using the ID transmitter.

Locking Procedure

After the vehicle door has been closed, the locking procedure is started by pressing the sensitive area on the outside door handle. The outside door handle electronics module sends the request to unlock the vehicle to the Car Access System 4.

The Car Access System 4 checks whether a valid ID transmitter is in the vicinity of the outside door handle using the outside antennas.

The ID transmitter is instructed to send an authentication signal.

In turn, the identification sensor sends encrypted data via the high-frequency link to the remote control receiver.

The remote control receiver processes the data and sends it via the LIN bus to the Car Access System. The Car Access System causes the communication with the ID transmitter to be established.

If the ID transmitter is recognized as belonging to the vehicle, the Car Access System 4 issues authorization for the vehicle to be unlocked.

The junction box electronics activate the central-locking drives.

Special Comfort Access Functions

The Comfort Access additionally features the special functions described in the following that are determined by the actions of the vehicle user.

Second ID Transmitter Remains in the Vehicle Interior

By checking via the interior antennas, the Car Access System 4 recognizes whether there is a valid ID transmitter in the vehicle interior. If the Car Access System 4 detects a valid ID transmitter in the vehicle interior and the vehicle is locked by means of another valid ID transmitter (located outside), the ID transmitter located in the vehicle interior is set to "blocked".

This ID transmitter will not be recognized as belonging to the vehicle for Comfort Access until the vehicle is unlocked again.

NOTE: The "blocked" status only applies to the functions of Comfort Access.

The remote control functions are still available.

Identification Transmitter in Luggage Compartment

If an ID transmitter is located in the luggage compartment when the vehicle is locked and the trunk open and the trunk is then closed, the trunk will immediately be automatically opened again. Audible and visual signals draw the customer's attention to the fact that the ID transmitter is located in the luggage compartment.

The Car Access System 4 starts the request via the luggage-compartment antennas.

If a valid ID transmitter is detected in the luggage compartment, the Car Access System 4 will not issue authorization for the trunk to be locked.

The trunk cannot be closed before the ID transmitter has been removed and is located outside the luggage compartment.

NOTE: This behavior only occurs if the Comfort Access does not find a valid ID transmitter in the vicinity of the vehicle when it searches the outside of the vehicle.

Starting the Engine without an ID Transmitter

This function makes it possible to start the vehicle within 10 seconds after "engine OFF" without detecting the ID transmitter. This function is intended for cases where, for example, the ID transmitter is not detected due to high-frequency interference.

Unintentional Wake-up Function

The vehicle cannot be woken simply by someone gripping the outside door handle. A valid ID transmitter must be detected in the vicinity of the vehicle.

Locking with Engine Running

The vehicle can also be unlocked with the engine running if the engine was started with Passive Go. When leaving the vehicle, the ID transmitter should also be taken and the vehicle locked from the outside.

Emergency Start Coil

In unfavorable situations, the ID transmitter cannot be found in the passenger compartment. The Car Access System therefore causes a message to be output to the instrument cluster. The message tells the customer that the ID transmitter could not be found.

Because there is no slot for the ID transmitter in the F01/F02, there is an emergency start coil on the steering column. Communication via the emergency start coil allows the engine to be started and the vehicle is then ready to be driven.

The emergency start coil has the same function as the transponder coil. Communication via the transponder coil makes it possible for the Car Access System 4 to identify the ID transmitter. The Car Access System 4 can issue the start authorization following successful identification.

The remote control or ID transmitter cannot be found in the following situations:

• Fault in the remote control/ID transmitter
• Interference in the transmission to the remote control/ID transmitter
• Flat battery in the remote control/ID transmitter.

Fig. 5: Identifying Emergency Start Coil

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