Keyless Entry: Description and Operation
66 01 05 (123)
Comfort Access
E65, E66
Introduction
The E65MU can also be equipped with option 322 "Comfort Access".
Comfort Access combines a high degree of functionality and comfort. The vehicle can be unlocked and the engine started without actively using a key.
Advantage:
Keyless access to the vehicle. It is enough to simply carry the ID transmitter (e.g. in your jacket pocket).
With Comfort Access, an ID transmitter is needed in place of the standard remote control. The ID transmitter also performs standard remote control functions.
Comfort Access can be used to carry out the following functions:
- Passive Entry: Access authorization
Opening the vehicle or luggage compartment without actively using the ID transmitter
- Passive Go: Drive authorization
Engine start without actively using the ID transmitter
- Passive Exit: Locking authorization
Closing the vehicle without actively using the ID transmitter
Comfort Access prevents an ID transmitter being disabled accidentally.
The CAS control unit is the master control unit for all functions carried out via Comfort Access. Vehicles with Comfort Access are fitted with a CA control unit.
Brief description of components
The following components are required for Comfort Access:
- Interior and exterior aerials
A total of 12 aerials are required for communication with the ID transmitter:
- 6 interior aerials: Driver's footwell and front-passenger footwell, rear-compartment footwell left and right, rear window shelf, luggage compartment
- 6 exterior aerials: outside door handle on all 4 doors, double aerial in rear bumper
The aerials emit 125 kHz radio signals which are evaluated by the ID transmitter.
- Outside door handle electronics
There is electronic circuitry in the outside door handle on all 4 doors.
The 3 sensors in the outside door handle electronics send the following signals to the CAS and CA control units:
- Start check: When a hand reaches into the handle recess via a capacitive sensor
- Unlock: When the outside door handle is pulled via a pull sensor
- Locking and deadlocking: When the outside door handle pressed via press sensor
A built-in aerial also sends radio signals in order to check for an ID transmitter located on the outside of the driver's door or front-passenger door.
- ID transmitter
The ID transmitter evaluates the signals from the aerials. It also sends high-frequency radio signals to the FBD receiver.
Inserting the ID transmitter into the insert compartment deactivates all Comfort Access functions.
- Remote control receiver
The remote control receiver (FBD receiver) is located in the right-hand C-pillar. The FBD receiver receives the radio signals from the ID transmitter and forwards them to the CAS control unit. The Comfort Access (CA) control unit activates the FBD receiver.
- Electric motor on door lock
Each of the 4 door locks also has an additional electric motor. The electric motor provides early release of the locking pawl in the door lock.
- Tailgate button
The tailgate button supplies a signal to the power module (PM) when the tailgate is opened. The power module sends the signal to the CAS control unit.
- START/STOP button
The START/STOP button can be used to switch the terminals in sequence (0, R, 15, R, 0). When the brake is depressed (automatic transmission) and the START/STOP button is pressed, the engine will start.
- Insert compartment for the ID transmitter/remote control
The remote control must be inserted into the insert compartment if the battery in the ID transmitter is discharged. The engine can then be started up.
Inserting the ID transmitter into the insert compartment deactivates Comfort Access.
Various control units are involved in the system:
- CAS: Car Access System
The CAS control unit is the master control unit for all Comfort Access functions. The CAS control unit is the interface to the START/STOP button and to the insert compartment for the ID transmitter.
The CAS control unit is connected with the following components via the K-bus (sub-bus):
- Electronic circuitry in the outside door handles of all 4 doors
- Comfort Access (CA) control unit
When the vehicle is idle, communication may take place on the K-bus without waking up the vehicle.
At the same time, the CAS also communicates with the CA control unit on the K-CAN PERIPHERY.
The sub-bus is activated when a signal is triggered from an outside door handle. If identification is negative, the sub-bus goes back into standby mode.
- TMFA, TMBF, TMFAH, TMBFH: 4 door modules
The door modules control the central locking. If the CAS control unit approves the unlocking of the vehicle, for example, the doors will be unlocked.
The Comfort Access sub-bus is simply looped through the door modules.
The "door handle pulled" signal is transmitted by the door module to the CAS control unit via the K-CAN PERIPHERY.
- CA: Comfort Access control unit
The Comfort Access (CA) control unit actuates the interior aerials and the two exterior aerials in the rear bumper.
An ID transmitter scan is carried out. At the same time, the FBD receiver is activated for any ID transmitters which may respond.
- PM: Power module
The tailgate button for opening the tailgate is connected to the power module. The signal is sent to the CAS control unit via the K-CAN PERIPHERY.
This means that the tailgate can also be opened individually.
System functions
Comfort Access is used to implement the following functions:
- Passive Entry via door
- Passive Entry via boot lid
- Passive Go
- Passive Exit
- Disabling an ID transmitter located inside the vehicle
- Disabling an opposing command
- Tamper-proof lock
Passive Entry via door
The vehicle is unlocked when the outside door handle is gripped or pulled. Condition: The ID transmitter must be located no further than 1.5 m from the aerial in the outside door handle.
Ideally, the user should carry the ID transmitter in a pocket.
First, the user is authenticated (= authenticity check).
The data transferred during the authenticity check is of course encrypted.
If the ID transmitter authenticity check is successful, the user will be granted access to the vehicle. The central locking is unlocked. The door can be opened.
Unlocking is supported by an electric motor for added comfort.
The same principle is applied for the authenticity check for Passive Entry and Passive Go.
Authenticity check using the example of Passive Entry:
- Trigger signal at outside door handle electronics via the capacitive sensor.
- Request sent to outside door handle electronics to locate an ID transmitter via the aerials in the outside door handle. All ID transmitters associated with the vehicle and located outside of it are included in the search (low-frequency radio signal at 125 kHz).
The search determines whether an ID transmitter associated with the vehicle is located in the operating range of the aerials in the outside door handle.
- At the same time, the outside door handle electronics send a message to the CAS control unit via the sub bus (K-bus).
- All ID transmitters located register with the CAS control unit by sending a radio signal via the FBD receiver (high-frequency radio signal, country-specific, e.g. 868 MHz).
- The CAS control unit decides which of the registered ID transmitters will be used for the subsequent authenticity check.
- This selection is sent to the outside door handle electronics in a message via the K-bus. At the same time, a request is sent to the outside door handle electronics to carry out a selective scan of the ID transmitter concerned.
- All ID transmitters not picked up in this scan end reception readiness for the communication operation currently in progress.
- The ID transmitter picked up via the selective scan responds by sending a radio signal to the CAS control unit via the FBD receiver (high-frequency radio signal at 868 MHz).
- The CAS control unit evaluates the response and, if it is valid, authorizes Passive Entry.
The vehicle is unlocked.
An electric motor unlocks the door lock early to enable the vehicle to be opened quickly enough. This ensures that the door unlocks whenever the user pulls the outside door handle to its full extent.
- The tension sensor is set up with redundancy to the capacitive sensor (e.g. capacitive sensor 1 deactivated due to long-term lack of use).
When the tension sensor detects the "Outside door handle pulled" signal, the door is unlocked. The door can be opened by pulling on the outside door handle again.
Passive entry via boot lid
Comfort Access can be used to open the luggage compartment without actively using the ID transmitter.
Condition:
The ID transmitter must be located no further than 1.5 m from the aerials in the rear bumper. Ideally, the user should carry the ID transmitter in a pocket.
To open the luggage compartment, the tailgate button must be pressed for approx. 500 ms. If an ID transmitter is located in the vicinity of the luggage compartment, the tailgate will open.
If an ID transmitter is located inside the luggage compartment when the boot lid is closed (and there are no authorized ID sensors outside the vehicle), the boot lid will open up again.
When this is done, the tailgate is fully opened by the force of a spring or by the automatic tailgate actuation (optional).
An ID transmitter inside the vehicle on the rear window shelf will also be recognized.
Passive Go
In order to switch the terminal and/or start up the engine, the ID transmitter must simply be located inside the vehicle (not necessarily in the insert compartment).
Engine start is not possible if an ID transmitter is detected inside the luggage compartment.
In principle, the authenticity check required is the same as that for Passive Entry (except that it is run via the interior aerials).
An ID transmitter must be located inside the vehicle when the START/STOP button is pressed. Otherwise, the instrument cluster will display a Check-Control message.
Press the START/STOP button to switch the terminals. The terminal switching sequence is as follows: 0 => Terminal R => Terminal 15 => Terminal R => 0.
The START/STOP button must be pressed for approximately 500 ms in order to start up the engine. On vehicles with automatic transmission, the brake pedal must be depressed at the same time.
The engine may be started up in any terminal position.
Once the engine has been switched off, it may be restarted within 5 seconds even if no ID transmitter is detected inside the vehicle (i.e. no valid drive authorization). This safety measure is required for possible emergencies.
Passive Exit
The outside door handle must be pressed to lock the vehicle and activate the anti-theft alarm.
If the outside door handle is pressed for approximately 3 seconds to lock the vehicle, the auto-remote closing (closing of the side windows or sliding/tilting sunroof and, if applicable, folding in of the door mirrors) is activated.
Auto-remote opening via the outside door handle is not possible.
Terminal R is deactivated when the outside door handle is locked.
Terminal 15 is not deactivated when the vehicle is locked. A Check-Control message appears as a warning when the driver's door is opened with terminal 15 ON.
Special feature: Comfort Access allows the vehicle to be locked whilst the engine is running.
Disabling an ID transmitter located inside the vehicle
When the vehicle is closed via the outside door handle, any ID transmitter inside the vehicle will be detected.
This ID transmitter is disabled for all Comfort Access functions.
However, it is still possible to access the luggage compartment. The ID transmitter is reactivated when the vehicle is unlocked again.
Disabling an opposing command
When the vehicle is unlocked via the outside door handle, it cannot be locked again for approx. 2 seconds.
Similarly, when the vehicle is locked via the outside door handle, it cannot be unlocked again for approximately 2 seconds.
This allows the user to pull on the outside door handle to check that the vehicle is actually locked.
Tamper-proof lock
The vehicle may only be locked and unlocked consecutively a maximum of 8 times. After this, the tamper-proof lock is activated.
Operation is disabled for 10 seconds. The tamper-proof lock is deactivated completely after 5 minutes. Once again, the vehicle may then only be locked and unlocked consecutively a maximum of 8 times.
Operation
How to use Comfort Access is described in the vehicle's Owner's Handbook.
Please note the following points concerning operation:
- Car wash
- Door-selective unlocking
- Absence of ID transmitter
Car wash
In the car wash, the ID transmitter must be inserted in the compartment provided while the engine is running. This prevents the parking lock from being automatically engaged (even with standard equipment without Comfort Access).
Door-selective unlocking
If door-selective unlocking is selected, only one door will be unlocked.
To unlock the other doors, press "Unlock" on the central locking button.
Absence of ID transmitter
The following exceptional circumstances could arise:
The engine must be running. The ID transmitter is removed from the vehicle.
Example: After changing drivers, the front passenger leaves the vehicle, taking the ID transmitter with him.
- The engine is not automatically switched off as an automatic engine shutdown is prohibited by law.
- If a door is opened and then closed again, a Check-Control message will appear.
- When the engine is switched off, the engine can be restarted within the space of 10 seconds.
This possibility is important, for example if the engine is switched off at a level crossing and there is no ID transmitter inside the vehicle
For safety, it is advisable to carry the spare key with you. In conjunction with the adapter, the spare key allows drive authorization. This means that the vehicle can still be driven, even without an ID transmitter.
Notes for service staff
Service staff should note the following points:
- General note:
- Diagnosis: ---
- Encoding/programming:
- Car and Key Memory:
Subject to change.