Car Access System
Car Access System
The Car Access System (CAS) control unit regulates access and the access options to the vehicle. The CAS control unit is the master control unit, e.g. for the following systems.
- Terminal control
- Electronic immobilizer
- Comfort Access (if equipment is present)
- Electric steering lock (if equipment is present)
- Central locking system
- Power window regulator
Brief component description
The following components for the Car Access System are described:
CAS: Control unit
The Car Access System (CAS) is the control unit that controls access to the vehicle (Comfort Access) and its functions (key identification, electronic immobilizer, release for engine start).
The CAS control unit is the master control unit for the power windows and central locking system functions. This means it checks the enable conditions before the junction box electronics control unit is permitted to activate the central locking system and the footwell module and junction box electronics control units are permitted to activate the power windows.
The CAS control unit is the master controller for the terminal control, i.e. it activates terminal 15, terminal 30B and terminal 50.
The electric steering lock is activated by the CAS control unit.
The CAS control unit evaluates the signals of the brake light switch and of the clutch module.
The CAS control unit is connected directly to the K-CAN2 (Body CAN2).
start/stop button
Together with the remote key, the START-STOP button is used to start the vehicle. The remote key contains an authorization code for the relevant vehicle.
Two hall effect sensors are installed in the START-STOP button. The hall effect sensors detect whether the START-STOP button is operated. When the CAS detects an authorized remote key, terminal 30B is switched on.
Pressing the start/stop button initializes the engine start. In the process, the CAS control unit checks the following prerequisites:
- With automatic transmission, selector lever position "P" or "N" and brake control
- With manual gearbox, clutch control
When all the prerequisites have been met, the engine is started by the CAS control unit in that terminal 50 to the starter motor is activated. To stop the engine, press the START-STOP button once again. The engine is switched off; terminal R remains switched on. On vehicles with automatic gearboxes, the engine can only be stopped with the vehicle at a standstill when the parking lock is engaged.
The START-STOP unit is connected via a 14 pin plug connection to the CAS control unit.
NOTICE: Emergency function during driving.
For safety reasons, the engine can be stopped during driving by pressing the START-STOP button. A renewed start in this case is possible without additional brake control or clutch control.
Electric steering lock
The electric steering lock (ELV) is an anti-theft system for vehicles with manual gearboxes.
The ELV is a control unit without a connection on the CAN bus. The ELV is supplied and activated by the CAS control unit. The CAS control unit is the master control unit for the electric steering lock (ELV). Faults of the electric steering lock (ELV) are stored in the CAS control unit.
After successful authentication of a valid key by the CAS control unit, the ELV is supplied with current to unlock it and terminal 15 is switched. Once the ELV has been unlocked and secured, the engine can be started by actuating the START-STOP button.
The CAS control unit checks the status information sent by the ELV. If the message after unlocking is not error-free information with the ELV status "ELV unlocked and secured", the CAS control unit is not allowed to grant starting approval and does not enable terminal 15.
The electric steering lock can only be locked when the vehicle is at a standstill and the engine is at standstill, too. After the door is opened or the central locking system is secured, the ELV is locked.
If no unlocking procedure or locking procedure is carried out, the electric steering lock is secured and without current.
The electric steering lock is connected to the CAS control unit via the body bus.
Remote control key and ID transmitter
The following functions (depending on the vehicle equipment) are triggered by the rechargeable remote control key or battery-operated ID transmitter with 3 or 4 buttons respectively.
- Opening and closing the central locking system
- Activation and deactivation of the anti-theft alarm system
- Deactivating the tilt sensor and interior movement detector
- Triggering the panic mode (if encoded)
- Unlock tailgate
- Opening and closing the tailgate
- Switching on the interior lighting
- Convenient opening and closing of the power windows and slide/tilt sunroof (if encoded)
Outside door handle electronics
The outside door handle electronics are located in the outer door handle of each door.
The 3 sensors in the outside door handle electronics send the following signals to the CAS control unit:
- Unlocking: When a hand reaches into the handle recess via capacitive sensor 1
- Unlocking: When a hand pulls on the outer door handle via pull sensor (redundant to capacitive sensor 1)
- Locking and deadlocking: On contact with the sensitive area of the door handle via capacitive sensor 2
A built-in aerial also sends radio signals in order to check for an ID transmitter located on the outer area of the driver's door or front passengers door.
Comfort Access aerials
Various aerials are required for communication with the ID transmitter: Interior and exterior aerials The aerials transmit on a frequency of 125 kHz. The wave emitted by the aerials are spherical in form. The ID transmitters are asked to identify themselves via the aerials. All the radio signals are encrypted and thus protected against unauthorized access.
Remote control receiver
The task of the remote control receiver is to pick up the radio signals, process these signals as well as to forward data to the CAS control unit. Further data processing as well as the corresponding function execution take place in the CAS control unit.
Notes for Service department
General notes
Redundant data storage:
If the instrument panel is replaced, the stored data (e.g. total distance reading) must be retained. This will make it possible to detect any evidence of manipulation. For protection against tampering, the following data are stored redundantly (second copy) in the Car Access System (CAS):
- Vehicle identification number
- Total distance (kilometer reading)
- Data for the scope of maintenance work of Condition Based Service (CBS)
The data is verified each time terminal 15 is switched on. A manipulation dot is shown in the LCD display in the event of any deviation. The manipulation dot appears to the left of the trip distance recorder on the instrument panel. The manipulation dot is displayed in the following cases:
- The vehicle identification number stored in the instrument panel is different to the one stored in the CAS control unit.
- A vehicle identification number is not stored in one of the two control units (e.g. new part).
- The module in the instrument panel for storing the total distance reading is faulty (the kilometer reading is shown as 999999).
Installing a new CAS control unit:
Order the new CAS control unit for the specific vehicle in question, quoting model code number, vehicle identification number, standard equipment. Once the new CAS control unit has been programmed and encoded (DME/DDE control unit and CAS control unit mutually identified and adjusted), the engine can be started.
IMPORTANT: Do not install a used CAS control unit. The engine cannot be started if the CAS control unit being fitted has already been used (different vehicle identification number).
Installing a new instrument panel:
The manipulation dot is set after terminal 15 is switched on because the vehicle identification number is not yet encoded in the instrument panel. Encode the instrument panel (enter the vehicle identification number in the instrument panel and assign it to the vehicle). Switch terminal 15 off and on. After terminal 15 has been switched back on: The current kilometer reading and the CBS data are transmitted to the instrument panel by the CAS. The manipulation dot is deleted.
Disable remote key:
The service function 'Remote key lock/enable' in the BMW diagnosis system can be used to lock or enable remote keys, ID transmitters or spare keys.
It is recommended that a remote key is disabled if it is lost or stolen. Engine start is not possible with a disabled remote key. The functions of the remote control buttons are also locked.
A remote key can only be locked if it has been used at least once and has not currently been authenticated by the CAS control unit as a valid key.
To run the service function, it is required that CAS control unit has currently detected a valid and enabled remote key.
Activating a new remote key:
A new remote key can be used immediately. For the first engine start, the remote key must be held at the ring aerial while the START-STOP button is operated. The ring aerial is fitted on the right side in the steering column shroud.
If the remote key is a replacement for a lost, stolen or defective remote key, the old remote key still has to be blocked using the service function "Block/release remote key". To use the Car/Key functions, the service function "Personalization number" has to be run.
Important information regarding the activation of spare keys
The following notes must be complied with:
- When reordering a number of infrared remote keys, they must be activated in the right order.
- When reordering a number of infrared remote keys, all infrared remote keys must be activated via the ring aerial.
- On ordering a new CAS control unit and new infrared remote keys, the new CAS control unit must be fitted first. The infrared remote keys may only be enabled after installation (keep to the right order).
- If a number of spare keys have been ordered or the CAS control unit has been renewed, it might be necessary to activate all keys at the ring aerial before all the keys work again.
Important notes on ELV (electric steering lock) diagnosis
If there is a fault in the electric steering lock, it can occur that terminal 15 is blocked by the CAS control unit (maximum value of the internal ELV frequency counter has been reached).
If terminal 15 is blocked, the diagnosis must be carried out in terminal 30B. To prevent the vehicle from going to sleep during the diagnosis, it must be kept awake. The vehicle is kept awake when the radio is switched on. During the diagnosis, leave the radio switched on. In terminal 30B, no automatic vehicle identification can be carried out at the start of the diagnosis. The vehicle has to be selected manually for identification.
The fault entries for the electric steering lock (ELV) are processed in the procedure AT6100_CAS4EV2 - Electric steering lock. If there are a number of fault entries for the ELV, all the fault entries must be processed in succession. For the fault cause to be found, all the instructions in the testing procedure must be followed precisely.
Notes on encoding/programming
IMPORTANT: After replacing the CAS control unit, it must be programmed and encoded.
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.