With the aid of the central locking the doors and fuel filler flap can be locked, secured and unlocked at central operating points and via the remote control. The general module or the central body electronics (ZKE III) controls the central locking system.
The central locking system can be operated via following operating points:
The vehicle can be locked and unlocked centrally by means of the ZV button in the vehicle (centre lock button).
A locked door can be unlocked and opened from the inside by pulling the door handle twice.
To avoid unintentional locking (lock-out) the ZV button is inoperable when:
A locked vehicle (arming after ignition OFF, opening/closing driver's door and locking via door lock or remote control) cannot be opened with the ZV button.
Two microswitches (= lock contacts) are switched by the lock cylinders in the front doors. These two contacts switch B+ to the door module of the corresponding door and signal ”lock/arrest” and ”unlock”.
There is no lock cylinder in the passenger's door if remote control is installed.
Note: On series E38 up to 9/95 the ”driver's door module” and the ”switch block for mirror and power window operation” are two separate control units. As of 9/95, the door module, driver's door is integrated in the switch block.
Up to September 1999, the central locking can be operated via the boot lid/tailgate lock.
Two microswitches (= lock contacts) are switched by the lock cylinder in the rear lid. These two contacts switch B+ to the general module and signal ”lock/arrest” and ”unlock”.
If the vehicle key is turned through 90o beyond the ”lock/arrest” position and removed (slot of cylinder lock horizontal) the rear (boot) lid remains locked even when the central locking system is unlocked from a different operating point (”hotel or workshop setting”).
Note: There is no cylinder lock in the boot lid on the series E39 touring.
As from September 1999, only one microswitch is fitted on the boot lid/tailgate lock which signals the lock positions ”unlock” or ”hotel or workshop position” via a line to the central body electronics control module. Signalling is necessary to ensure no alarm is triggered with the antitheft alarm system armed when the boot lid/tailgate is unlocked with the vehicle key and the boot lid/tailgate cannot be opened electrically via the remote control or button in the ”hotel and workshop position”.
A differentiation must be made between two central locking statuses on all vehicle doors:
When locking, the locking button is pulled downward. The door can no longer be opened from the outside with the door handle. The door can be opened from the inside by pulling the door handle twice.
The driver's door remains unlocked if the vehicle is locked with the driver's door open.
A locked vehicle can be unlocked from the inside by means of the ZV button.
When arresting, the rotary latch lock is uncoupled internally from the opening mechanism. The door can be opened neither from the outside nor from the inside. The ZV button is inoperable.
The vehicle is locked and arrested automatically by operating the central locking system via the lock cylinders or by remote control when the ignition lock is in position 0 (terminal R and 15 switched off) and the driver's door was opened and closed at least once after switching off terminal R.
The front central locking drives are driven by means of transistors in the relevant door modules. The rear door drives and fuel filler flap are driven by means of a relay in the general module.
The central locking drive consists of an electric motor and an integrated microswitch (= position switch). The rotary movement is transmitted by means of a gear system to the mechanics of the rotary latch.
After activation of the central locking system, the electric motor is switched on until the position switch in the drive reaches the ”locked” position. If the doors are to be arrested, the electric motor is activated once again and the gear mechanism is moved beyond the ”locked” position into the ”arrest” end position.
Overloading due too frequent operation must be avoided since the electric motors in the central locking drives are blocked in the end position (in arrest position). For this reason, the central locking system is blocked by a lock-out function if operated 32 times within 2 minutes such that a function is carried out only every 4 seconds.
The repeat lock-out is cancelled after 3 minutes.
For reasons of safety, the central locking is unlocked if the basic module recognizes an accident (crash). The impact is recognized:
In addition to unlocking the doors, the hazard warning lights and the interior lighting are switched on.
Crash recognition is switched off when the ignition lock is in position 0 or the central locking in the ”arrested” position.
The door mechanism is uncoupled from the ZV drive when an electrically locked door is unlocked mechanically by means of the inner door handle (door handle pulled twice). The lock mechanism and ZV drive assume an opposing status, i.e. they are asynchronous.
The general module recognizes this asynchronous status by means of the door contact signal which indicates that the door is open.
The next time the central locking system is locked electrically, the door is re-synchronised automatically, in that, after being locked, the system unlocks and then locks again.
In various country versions (e.g. USA), ”selective unlocking” is coded in the general module. In this setting, initially, only the driver's door is unlocked when unlocking for the first time via the lock contact or remote control. The remaining doors are set from the position ”arrested” to ”locked” so that they can only be opened by means of the inner door handle.
All doors are unlocked when the vehicle is unlocked a second time.