
Central Locking
Purpose of the System
The  Central  Locking  System  provides  locking/
unlocking  of  the  entire  vehicle  from  one  central
exterior  point.  From  the  driver’s  door  or  the
remote (key-less) entry, a lock/unlock request will
lock/unlock all exterior doors, luggage compart-
ment and the fuel filler flap.  
From inside, the vehicle can be locked/ unlocked using a cen-
tral  locking  button  located  in  the  center  console. Individual
doors can be unlocked manually by pulling twice on the inte-
rior door handle. 
From 2000 MY
- if the vehicle has been double locked, press
the central locking button and pull the interior door handle
twice (alarm will sound when the door opens).
Locking the vehicle from the central switch will “single lock” all
doors, luggage compartment and not lock the fuel filler flap.
The Central Locking System utilizes the GM III and Door Modules to carry out all of the lock-
ing/unlocking features: 
• Remote (key-less) entry is standard.
• When locked from the outside, the vehicle will double lock and arm the DWA System. The  
ignition must be switched off and the driver’s door must be opened and closed. 
• Selective  unlocking  from  the  outside  of  the  vehicle.  Unlocking  from  the  driver’s  door  or
remote transmitter will only unlock the driver’s door and disarm the DWA System. A sec-
ond request will unlock the remaining doors and luggage compartment. This feature can
be modified for individual users in Key Memory to open all doors from a single request. 
• A single central locking button is installed in the center console that will operate when all
of  the  doors  are  closed.  Locking  the  vehicle  from  the  central  switch  will  “single  lock”  all
doors,  luggage  compartment  and  not  lock  the  fuel  filler  flap.  When  unlocking,  a  single
request will unlock the driver’s door only. This feature can be modified for individual users
in Key Memory to open all doors and luggage compartment from a single request.
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• A  remote  luggage  compartment  button  is  installed  in  the  left  kick  panel  (center  console
in the E53) to open the luggage compartment from inside the vehicle.
• The EWS is interfaced for double lock monitoring and unlock function. With the presence  
of an accepted EWS key in the ignition, the vehicle will be unlocked and disarm DWA.    
• The automatic locking feature (> 99 MY) activates the door locks when a road speed 
signal of 5 MPH  and engine RPM is detected via the K-Bus. The factory default setting 
of this feature is off (can be encoded on for individual users with Key Memory function).
• In the event of an accident (ignition on), the GM will be signalled to unlock all doors.
Hardware Features:
• The external lock cylinders are located in the  
driver’s door and luggage compartment lid   
(E53/E39 Sport Wagon does not have a tail- 
gate lock cylinder).
• The driver’s door and luggage compartment   
incorporates an overrunning lock cylinder. The  
lock cylinder will free wheel or spin If any key  
other than the vehicle key or tool, such as a  
screw driver, is inserted into the cylinder. The 
lock cylinders can be manually locked/un- 
locked  by turning the key “past” lock/unlock.
• The door lock buttons are mechanically uncoupled from the  
lock actuators when locked. 
The door lock buttons “mechanically” lock the individual 
doors. This provides manual locking in the event of a central  
locking malfunction.
• Child safety locks (located in 
the rear doors) are  actuated 
by inserting a key in the slot on  
the door latch or by sliding a  
lever (dependent on model). 
The door can now only be  
opened from outside.
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Door
Button
Lock
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• The luggage compartment can be manually   
locked with a “Master Key” and leaving the  
lock cylinder in the horizontal position which 
prevents opening by any other method (sec- 
ured for valet).
The luggage compartment release button in-  
side the vehicle will also be ignored by the GM.
Prior to 2000 MY the vehicle could be locked/ 
unlocked using the luggage compartment lock 
cylinder. 
• The glove box has a lock cylinder to secure the  
contents by manual locking with a “Master 
Key”  and leaving the lock cylinder in the hori-
zontal position which prevents opening by any 
other method (secured for valet). 
• The E38 has a lever behind the glove box han
dle which permits locking the glove box with-  
out a key. Opening still requires a key.
The valet key is not mechanically capable of
entering either of these lock cylinders.  
• The Fuel Filler Flap mechanical release is found 
in the right side of the luggage compartment.  
The “pull tether” is behind the button as shown  
on the right. 
Note:  Continuous  operation  of  locking/unlocking  will  cause  a  timed  arrest  of  the
locking  system.  When  activated,  the  timed  arrest  lasts  for  2  minutes  (or  recycle
the ignition KL15). The “crash” signal will override the timed arrest and unlock the
vehicle.
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System Components 
- with the Principle of Operation
Driver’s  Door  Lock: The  lock/unlock  signals
from  the  driver’s  door  lock  cylinder  are  input  to
the  driver’s  door  module  from  the  two  micro
switches  on  the  lock  cylinder.  The  driver’s  door
switchblock module carries out the locking func-
tion of the driver’s door.  
The  windows  and  sunroof  can  be  closed  or
opened  by  holding  the  key  in  the  lock/unlock
position (convenience closing/opening feature). 
The  signal  to  lock  the  remaining  doors  and  fuel  filler  flap  is  passed  over  the  P-Bus  to  the
GM III and passenger’s door module. The locking of the passenger’s door is carried out by
the  passengers  door  module.  The  rear  doors,  luggage  comparment  and  fuel  flap  locking
are carried out directly by the GM III. All four doors will be pulled into the double lock posi-
tion when locking from the driver’s door.
The control of the actuators in the front doors is through final stages in the door modules.
The rear doors, trunk and fuel filler flap actuators are controlled by internal relays in the GM
III. When locked, the GM III will not carry out any opening commands from the central lock-
ing button or luggage comparment interior release button.
Luggage  Compartment  Lock  Cylinder  (except  E53/E39  Sport  Wagon): The  vehicle
can be locked/ unlocked (prior to 2000 MY) from the luggage compartment lock cylinder.
The lock/unlock micro switch inputs are processed in the GM III and the locking commands
are carried out. 
The signal is passed over the P-Bus to the
door  modules  to  lock/unlock  the  front
doors  and  the  GM  III  locks  the  rear  doors
and fuel filler flap. 
All door actuators are placed in the double
lock position. Removing the key in the hor-
izontal position will activate the valet mode
and prevent the valet key from opening the
luggage comparment.
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Luggage Comparment Remote Unlock: The luggage com-
parment  can  be  opened  from  inside  the  vehicle  with  the
remote release button. This feature is also functions when the
doors are locked from the central button. 
The  GM  will  disregard  the  remote  release  button  input  when
the  luggage  comparment  is  mechanically  locked  with  the
Master Key (valet setting). 
The  GM  will  also  disregard  the  release  input  if  the  vehicle
speed is > 4 MPH.
The  E53  remote  release  button  is  located  in  the  center  con-
sole. This input will release the rear liftgate following the same
criteria stated above.
Crash Signalling
The Multiple Restraint System (MRS) control module provides a switched signal to the GM
in the event of an accident. This signal was previously provided by the crash sensor locat-
ed in the left front kick panel (< 9/96 MY). 
The signal is an output function of the MRS control module and becomes active when MRS
determines  a  crash  has  occurred.  The  GM  unlocks  the  vehicle,  switches  on  the  interior
lights and flashes the exterior lights when this signal is active.
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Door Lock Actuators: A door lock actuator contains an electric motor and an integrated
microswitch (position switch). The rotary motor movement through the gear drive mechan-
ically moves the locking latch.
When the lock actuator is operating, the motor is powered until the position switch signals
the “locked” position. If the vehicle is locked from the exterior, the motor is powered further
and  the  the  gear  mechanism  is  moved  beyond  the  locked  position  into  the  “double  lock”
position.  The  motors  must  be  powered  (in  reverse)  to  release  the  double  lock.  The  inside
door handles will not unlock a “double locked” vehicle.      
E53  Door  Lock  Mechanism: The  E53  utilizes  a  door  latch  combined  with  dual  actuator
motors. This type of actuator is sealed, self contained units with no replaceable parts. The 
door lock actuators use hall effect sensors in place of pin contacts/microswitches to pro-
vide:
• Door lock key position (driver’s door only)
• Door open/closed status (replaces door jamb  
switch).
The GM monitors the lock cylinder positions over two
wires.  The  signals  are  generated  by  two  hall  effect
sensors (Hall Sensor 1 & 2) located in the actuator. 
When  the  key  is  turned,  a  plastic  cylinder  in  the  lock
actuator is simultaneously rotated by the lock tumbler
extension rod. 
An asymmetrical shaped magnet is incorporated in the plastic cylinder, which when rotat-
ed changes the magnetic influence on the hall sensors. The presence of a magnet in close
proximity  to  the  sensing  surface  of  either  hall  sensor  creates  a  coded  input  over  the  two
wires that the GM uses to determine the key position.
• Magnet in front of sensor, current flow through the sensor is <5 mA (0). 
• Magnet rotated away from sensor, current flow through the sensor is >12 mA (1).
Hall  effect  sensors  improve  the  actuators  reliability  since  they  are  impervious  to  moisture
and there are no wear contacts.
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• Key  in  the  neutral  position,  both  sensors  are
simultaneously  influenced  by  the  magnet  -
0/0.
• Key  turned  to  the  unlock  position  from  neu-
tral,  hall  sensor  #1  magnet  segment  moves
away from hall sensor - 1/0.
• Key  turned  to  lock  position  from  neutral,  hall
sensor  #2  magnet  segment  moves  away
form hall sensor - 0/1.
There  are  two  motors  incorporated  in  each  actuator
that provide two separate functions:
Single  lock/unlock  function:  Also  known  as  central
lock,  this  motor  controls  the  mechanical  lock  mecha-
nism when the central lock button is pressed to single
lock the vehicle. 
The lock mechanism is fully locked at this point but can
still be opened from the interior by pulling the appropr-
iate interior door handle twice or by pressing the cen-
tral lock button again. When single lock function is acti-
vated, the fuel filler flap actuator is not locked.
Double lock/unlock function: Also known as central
arrest,  this  motor  is  activated  only  when  the  vehicle  is
locked from the exterior at the driver’s door lock with a
key  or  when  the  GM  receives  a  lock  request  from  the
Key-less  entry  system.  In  this  case  the  double  lock
motor  is  activated  simultaneously  with  the  single  lock
motor. 
The  function  of  the  double  lock  motor  is  to  mechani-
cally offset an internal rod disabling it from unlocking 
the vehicle from the interior. This prevents the doors  
from being unlocked by any means except from an  
unlock request at the driver’s door or via the Key-less  
entry.
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HALL SENSOR 1
HALL SENSOR 2
PLASTIC CYLINDER
WITH ASYMMETRICAL MAGNET
(Shown in the Lock Position)
SINGLE
LOCK
MOTOR
DOUBLE
LOCK
MOTOR
ACTUATOR IN UNLOCKED POSITION
ACTUATOR IN LOCKED POSITION
WHEN IN DOUBLE LOCK AN
INTERIOR ACTUATED UNLOCK
ROD IS OFFSET PREVENTING
THE LOCK MECHANISM FROM
BEING MECHANICALLY
UNLOCKED 

Door Contact Hall Sensor: Also included in the drivers door actuator is a third hall effect  
sensor. This sensor signals the door open/closed status to the GM. This sensor replaces 
the door jamb mechanical switch of previous systems. The rotary latch plate position acti- 
vates the door contact hall sensor.
• When  the  door  latch  is  closed,  current  flow
through the sensor is <5 mA (0).
• When  the  door  is  open,  current  flow  through
the sensor is >12 mA (1). 
The  passenger  side  front  door  and  both  rear
door lock actuators only include this hall effect
sensor  (hall  sensor  3).  Hall  sensors  1  &  2  are
not required. 
Trunk  Lid  Close  (E38  SCA)/Tailgate  and  Window  Latching  System  (E39/E53): The
tailgate/trunk lid is opened by any of the three input signals: FZV, remote button and unlock
switch pad (push - trunk lock cylinder E38).  
These inputs request the rear latch
actuator  control  circuit  to  be
switched  to  ground  (exception:
presence  of  road  speed  signal,
key on with FZV request.)
The  rear  latch  actuator  unlatches
the  mechanism  and  signals  the
GM  of  the  open  latch  status.  The
SCA  motor    rotates  the  striker
180
O.  Feed-back  signalling  stops
the motor. E38 - When closing the
trunk lid the trunk latch micro-
switch signals the GM to activate
the SCA motor to pull the lid
down.
Rear window unlatching is requested by the rear window switch ground signal. This signal
initiates activation of the rear window actuator relay control circuit which activates the rear
window  actuator.  The  actuator  unlatches  the  mechanism  opening  the  window.  The  latch
simultaneously  provides  an  open  window  signal  for  the  rear  window  wiper  motor  module
as well as an interior light on request (via the wiper module). 
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Shown
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