Car Access System (CAS)
Car Access System (CAS)
Car Access System
The Car Access System (CAS) regulates the access options to the vehicle. The CAS control unit is the master control unit, e.g. for the following systems.
- Electronic immobiliser
- Central locking system
- Comfort Access
- Electric steering lock
- Power window regulator
The MINI is also fitted with a fixture for the remote key and a START-STOP unit with the START-STOP button.
The electronic immobiliser is a further development (4th generation).
Brief component description
The following components for the Car Access System are described:
CAS control unit
The CAS control unit is the master control unit for the systems listed above. The CAS control unit is the interface to the START-STOP unit with a fixture for the remote control. The electric steering lock is also activated by the CAS control unit. The CAS control unit is directly connected to the K-CAN (body controller area network). The electric steering lock is connected to the CAS through the body bus.
The fourth generation electronic immobiliser is integrated in the Car Access System.
The START-STOP unit is connected via a 14 pin plug connection to the CAS control unit. The START-STOP button and the remote key fixture are integrated in the START-STOP unit.
START-STOP button and fixture for remote key
The START-STOP button and the remote key together start the vehicle. The remote key contains an authorisation code for the corresponding vehicle.
After inserting the remote key in the fixture, the transponder authorisation is read out. When the CAS detects an authorised remote control, terminal R is switched on. At the same time, the remote control is locked in the holder. The interlock is locked by a solenoid switch. The locked remote key is a prerequisite for the terminals to be switched (terminal R, terminal 15 with engine ON/OFF). An interlock prevents the remote key from being pulled out under the following preconditions:
- Engine running
- Speed signal greater than 0 km/h
- Selector lever not in "P" (park) for automatic vehicles
Pressing the START/STOP button initialises 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
Once all prerequisites have been met, the engine is started by the CAS control unit (terminal 50 activation). The engine is stopped by pressing the START-STOP button once again. The engine is stopped, terminal R stays switched on (for a long press, terminal 30). On vehicles with automatic gearboxes, the engine can only be stopped with the vehicle at a standstill when the parking lock is engaged. This fully electronic access to the vehicle has the following advantages:
- increased reliability of the terminal signals from wear-free sensor system
- defined switching characteristics of terminal outputs
- electronic access option to vehicle e.g. for auxiliary heater and Telestart (remote engine start)
NOTICE: Emergency function while driving.
For safety reasons, the engine can be stopped while driving by pressing the START-STOP button. A renewed start in this case is possible without additional brake control or clutch control.
NOTICE: Engine start for Comfort Access.
For Comfort Access (CA), the remote key must not be in the fixture when starting the engine.
Electric steering lock
After authentication by the CAS, the electrical steering interlock is supplied with current. Only now can the steering be unlocked or locked. An engine start is only permitted when the electrical steering interlock has been unlocked and secured.
The electric steering lock can only be locked when the vehicle is at a standstill and the engine is at standstill, too. If no unlocking procedure or locking procedure is carried out, the electric steering lock is secured and without current.
System functions
The following system functions are described for the Car Access System (CAS):
- Terminal control
- Electronic immobiliser
- Comfort start
- Control of the electric steering interlock
- Remote control of the central-locking system
- Central control of the central locking system
- Central control of the power windows
- Central control of Comfort Access (CA)
- Waking the MOST via the K-CAN for a Telematic service
- Central data source for the vehicle order and redundant data storage for vehicle data
Terminal control
The CAS activates the following terminals via the START-STOP unit as follows:
- Terminal R
To maintain the starting capability of the vehicle, the CAS switches terminal R off automatically. if the driver's door is opened and closed and no seat occupancy is detected, terminal R will be switched off after 8 minutes.
- Terminal 15
The CAS controls terminal 15 (= active positive) for all electrical systems.
- Wake-up line (terminal 15 wake up)
Switching on terminal 15 activates (wakens) the control units on the PT-CAN via the wake-up line.
- Terminal 50L
During the starting operation, terminal 50L is connected to the starter.
- Switched terminal 30g
Some consumers (e.g. SHD, DSC) are attached to terminal 30. Terminal 30 is switched by the CAS. Shutting down the consumers on terminal 30g reduces the off-load current.
Electronic immobiliser (petrol engines)
The electronic immobiliser is both an anti-theft system and start enable device. On the MINI, a newly developed electronic immobiliser (4th generation) will be introduced. This new development uses a new and modern encryption method. Each vehicle is assigned a 128-bit secret code. This secret code is stored in a BMW database.
This means that the secret code is only known to BMW. The secret code is programmed into the CAS control unit and DME control unit and is locked. When the secret code is in the control units, it can no longer be deleted or changed. This means that each control unit is assigned to a certain vehicle. The CAS control unit and the EWS control unit identify themselves with the same secret number and an algorithm.If the identification data is correct, the CAS control unit activates the starter motor via a relay in the control unit. At the same time, the CAS control unit sends the DME control unit an encoded enable signal (rolling code) for the engine start. The DME control unit only enables the engine start if a correct enable signal is received from the CAS control unit. These operations may result in a slight delay in starting (up to half a second).
NOTICE: Procedure in case of defective control unit.
If the CAS or DME is defective, a certain procedure must be followed. The required control unit must be ordered exactly for the vehicle. For this, the vehicle data (vehicle identification number) is required. An EWS adjustment is not necessary after renewing the control unit.
Convenient starting
Pressing the START-STOP button initiates the starting operation. The starter motor is only activated until the engine is running. If the engine does not start, the starting operation is aborted after approx. 60 seconds. The START-STOP button only picks up drivers requests. The starting operation is carried out by the CAS control unit.
The CAS only performs the engine start when all the start conditions have been met. If a precondition is no longer met during the starting operation, the starting operation is aborted.
Control of the electric steering interlock
During the unlocking procedure, an authentication procedure is run between the Car Access System (CAS) and the electric steering lock. The electric steering lock may only commence unlocking after a positive result in the authentication procedure. For safety reasons, the electric steering lock is not supplied with current while the vehicle is being driven. The electric steering lock is only supplied with voltage for the unlocking procedure or locking procedure.
Unlocking the electric steering lock
The unlocking procedure starts when terminal R is switched on. After recognition of valid access rights, the CAS triggers the operation for unlocking the electric steering lock. First, the CAS switches the electric steering lock on. The vehicle condition and the status of the electric steering lock are then checked. Finally, the encoded signal is sent to release the lock. Once it has received the valid authorisation, the electric steering lock initiates the unlocking procedure. The electric steering lock drive is actuated to "unlock".
The motor moves a driver via a single-stage gear. The driver pulls the locking bolt into the unlocked position until the locking lever locks into place. The end position of the locking lever is picked up by a Hall sensor. The motor stops when the electric steering lock detects the "unlocked and deadlocked". This status is sent via K-CAN to the CAS. The CAS interrupts the power supply. In the current-free state, the locking lever is locked automatically.
NOTICE: Start enable by Car Access System.
Start enable is granted by the CAS control unit. A start enable is only granted after an error-free plausibility check. The CAS control unit must detect the status "unlocked and secured" without errors. For an engine start, the CAS must have switched off the power supply to the electric steering lock.
NOTICE: Unlocking for Comfort Access
For vehicles with Comfort Access, the remote key is also an ID transmitter. A valid ID transmitter must be detected inside the vehicle for the electric steering lock to be unlocked.
To lock the electric steering lock:
When all the conditions for locking have been met, the CAS initiates the locking procedure. The CAS switches the power supply for the electric steering lock on and checks its status. When the status has successfully been validated, the CAS sends the lock enable signal to the electric steering lock. The locking procedure is started. The motor moves a driver via a single-stage gear. The driver pulls the locking bolt in to the lock position until the locking lever engages. The end position of the locking lever is picked up by a Hall sensor. If the electric steering lock detects the position "not unlocked and secured", the engine is stopped. This status is sent via the body bus to the CAS. The CAS interrupts the power supply. When no current is applied, the locking lever is automatically locked. If the electric steering lock has already locked without errors, no locking procedure is executed. The electric steering lock once again sends the current status to the CAS control unit.
NOTICE: Lock only after vehicle standstill.
The electric steering lock is only activated if the following signals indicate that the vehicle is stationary:- Speed signal on the serial interface.- Signal on the driving condition on the CAN bus.
Both signals must indicate the vehicle is at a standstill. This plausibility check only takes place for the locking procedure.
Locking for Comfort Access
For Comfort Access, the vehicle is locked if the button on the outer door handle is pressed. Here, the electric steering lock also locks. On vehicles with Comfort Access, the electric steering lock locks if the engine has been started and the following conditions are satisfied:
- Terminal 15 off
- Locking via the button in the outer door handle
If the engine has not been started, the electric steering lock will lock after terminal R has been switched OFF and a door opened. Or secure on vehicle if terminal R was ON.
Central control of the central locking system
The CAS control unit is the master control unit for the central locking system. Depending on the control request, the CAS decides whether the central locking should be unlocked, locked or deadlocked.
NOTICE: Deadlocking for specific national-market versions only.
There is no deadlocking motor for US versions.
The central locking system for the doors, tailgate and fuel filler flap is activated by the junction box electronics (JBE).
Central control of the power windows
The CAS is the master control unit for the power windows. Because of the various national versions, the functions of the power windows are heavily dependent on the encoding.
The door power window regulators are activated by the footwell module (FRM).
Central control of Comfort Access (CA)
With Comfort Access, an ID transmitter is required instead of the usual master key. The ID transmitter also performs standard master key functions. Comfort Access can be used to carry out the following functions:
- Access authorisation
Opening the vehicle or luggage compartment without active use of the ID transmitter
- Drive authorisation
Engine start without active use of the ID transmitter
- Locking authorisation
Closing the vehicle without active use of the ID transmitter
The CAS control unit is the master control unit for functions run by Comfort Access. On vehicles with Comfort Access, a CA control unit is fitted.
Central data source for the vehicle order and redundant data storage for vehicle data
The vehicle order is stored in the CAS. The vehicle order describes the type of vehicle, national version and optional extras. The following are stored in the CAS control unit (redundantly to the instrument cluster):
- Vehicle identification number
- Status of the odometer
- Data for Condition Based Service (CBS)
The vehicle identification number and odometer serve to prevent manipulation. The CBS data is important for regular maintenance in service. The CBS data must not be lost. The CBS data is updated within a drive cycle in the ignition key or remote control.
A drive cycle is defined by:
- The first update is carried out when:
- Terminal 15 ON
- and speed above 41 km/h at least once and
- and speed drops back to below 39 km/h
- Every other update is carried out when:
- a distance of more than 10 kilometres is driven
- and speed above 41 km/h at least once and
- and speed drops back to below 39 km/h
A hidden service function can also be used to update the CBS data on the remote key:
- Insert remote control -> Press and hold centre lock button -> Switch on terminal 15
Notes for Service department
General notes
NOTICE: Hidden service function in an emergency.
In the event of a fault in the latch mechanism, there is a hidden service function to switch on terminal R. This can prevent breakdowns. Press the START-STOP button for 10 seconds.
Diagnosis instructions
Note the following information for diagnoses on the Car Access Systems:
Checking the remote key
The remote key can be checked using the diagnosis system. If the remote key is inoperative, proceed as follows:
- First check whether another remote key belonging to the same vehicle works
- Check the remote key battery charge
- Measure the electrical field strength
The electrical field strength of the remote key can be measured using the diagnosis system and the control unit functions of the CAS. A button on the remote key must be pressed to take the measurement. If a value for the field strength is read out, this means that:
- the transmission distance between the remote key and the remote control receiver is OK, no sources of interference detected.
- the signal line from the remote control receiver to the Car Access System (CAS) is OK.
NOTICE: Decreasing field strength.
As the remote key moves further away from the vehicle, the measured field strength drops.
Notes on encoding/programming
The following steps must be taken after replacing the Car Access System (CAS):
- Program the CAS
- Encode the CAS
- For diesel engines: Carry out an adjustment with the DDE
The adjustment between the CAS and the Digital Diesel Electronics (DDE) is among the service functions. During the adjustment, the rolling codes for the electronic immobiliser (EWS, 3rd generation) are initialised.
National-market version
There is no deadlocking motor for US versions.
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.