Car access system (CAS)

Functional description, see BMW Technology:

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Service functions

Replacing control units

The following points must be borne in mind when the CAS or the engine control unit are replaced:

• If a CAS control unit is replaced, it must be ordered using the vehicle identification number (VIN). Following installation, that starting value must be adjusted to the engine control unit. This starting value adjustment is performed using the service function ”DME/DDE - CAS calibration” in the BMW diagnosis system.
  
• If the engine control unit is replaced, the drive-enable code must be transferred from the CAS to the engine control unit following installation. This operation is also performed using the service function ”DME/DDE - CAS adjustment” in the BMW diagnosis system.
  
• After the adjustment of the EWS and engine control unit, these are mutually linked. It is not possible to replace one of the two control units as a test.
  

DME/DDE - CAS adjustment

In the case of a new engine control unit, the service function ”DME/DDE - CAS adjustment” in the BMW diagnosis system is used to read the EWS drive-enable code from the CAS and transfer it into the engine control unit. This means that the engine control unit and the CAS control unit are mutually linked.

If the engine control unit is already linked to the CAS, the service function is used to perform a starting value calibration. This means that the random code calculation between the CAS and the engine control unit is calibrated.

A start calibration is required if there is a variance in the random codes caused by the influence of errors in the two control units.

As of EWS4, a start calibration is no longer required.

Locking the remote control/spare key

The service function ”Remote control/Lock/Enable Key” in the BMW diagnosis system can be used to lock or enable remote control keys or spare keys.

The locking is recommended when a remote control key or a spare key is lost or stolen. With a locked remote control key (or spare key), the engine cannot be started. The functions of the remote control are also locked.

A remote control key or a spare key can only be locked if the remote control key or spare key has been used at least once and it is not inserted in the ignition lock.

To perform the service function, it is required that a valid and enabled remote control key or a valid and enabled spare key is detected in the ignition lock.

Activating a new remote control

Insert the new remote control in the slot and hold in this position until the remote control locks into place. This can take up to ten seconds. After locking, wait another five seconds. The remote control is then ready for use.

If the remote control is a replacement for a lost or defective remote control, the old remote control still has to be blocked using the service function ”block/release” (see above). To use the Car/Key functions, the service function ”Personalisation number” has to be run.