
Table of Contents
SubjectPage
Central Body Electronics (ZKE III)  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Objectives of the Module  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Purpose of the System  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
System Components  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Power Distribution  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Windshield Wiping/Washing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Headlight Washing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Rear Window Wiper/Washer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Rain Sensor  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Central Locking. . . . . .  . .  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Trunklid/Tailgate  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Remote (Keyless) Entry.  . .  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Car Memory/Key Memory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Anti-Theft (DWA) System . .  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Power Windows/Sunroof . .  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Interior Lighting. . . . . . . . .  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Visual Entry Aid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Seat/Mirror/Steering Column Memory. . . . . . . . . . . . . . . . . . . . . . . . . . 58
Seat Functions  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Steering Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
General Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75
Consumer Cut Off/Overload Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Sleep Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Review Questions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 

3
Central Body Electronics ZKE III
Central Body Electronics (ZKE III)
Purpose of the System
The Central Body Electronics (ZKE III) system manages the following functions:
GM III
• Windshield Wiping/Washing
• Windsheild Rain Sensor (AIC)
• Headlight Washing
• Tailgate Wiping/Washing
• Interior Lighting
• Central Locking
• Keyless Entry
• Key Memory
• Power Trunk Release
• Electric Opening of Tailgate
• DWA Alarm System
• Servotronics
• Consumer Cut-off/sleep mode
• DiagnosisDriver’s Door Switch Block/
Module
• Power Windows
• Mirror Adjustment/Memory/   
HeatingPassenger’s Door Module
• Mirror Adjustment/Memory/
Heating
• Power Windows
Sunroof Module
• Power SunroofSeat/Mirror/ Steering Column
Memory Module
• Seat Adjustment/Memory
• SteeringColumn Adjustment/
Memory
The ZKE III system was introduced on the E38 and is used in the E39 and E53. Most of the
functions  operate  the  same  on  these  vehicles  with  minor  changes  and  added  features  to
the system.
ZKE III  represents  the  combination  of  Body  Electronics  functions  into  one  central  control
module, the General Module (GM).  

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Central Body Electronics ZKE III
The following is an overview of new or changed features found on the E53 ZKE III variant: 
• Passenger’s door module is incorporated into the passenger’s door switchblock.
• Sunroof module (SHD) is located on the P -Bus.
• The Central Locking system uses a door lock actuators with hall effect sensors.
• The GM III is responsible for the Key Memory feature.
The E53 ZKE III system continues to be a modular system consisting of the following:
•General Module III  = Main controller for ZKE functions
•PM - SB/FT             = Driver’s door switch block and door module
•PM - SB/BT            =Passenger’s door module/Window switch
•PM - SHD               =Sunroof module
•PM - SM                 =Seat/Mirror/ Steering Column memory module
•AIC                         = Rain Sensor (if equipped)
All of these modules communicate over the “K-Bus and P-Bus” for signaling purposes and
diagnosis. 

Rear  Window  Wiper/Washer  System  (E39  Sport  Wagon  and  E53): The  system  is
included in the scope of ZKE however is not controlled directly by the GM. The control elec-
tronics are integrated into the rear wiper motor assembly. The control electronics contains
two hall sensors, one for monitoring park position and other for the end stop, or to signal
reverse  direction  of  the  wiper  motor.  The  control  electronics  are  connected  to  the  vehicle
electrical system via a single seven pin connector.
The  rear  wiper  system  is  operator  controlled
through the wiper stalk switch providing the fol-
lowing functions:
• Intermittent rear window wiping
• Programmed rear window wiping interval
• Operation of the rear window washer
Pressing the wiper stalk forward to the first detent activates the rear wiper in the intermit-
tent mode
. The timed interval is approximately 7-12 seconds. The full sweep and park posi-
tions  are  recognized  by  the  two  hall  sensors  on  the  motor  gear  assembly.  If  the  wiper  is
switched OFF, the wiper blade will return to the park position.
The programmed wiper interval procedure is as follows:
• Briefly switch the rear wiper ON/OFF
• Wait the desired interval time
• Switch the rear wiper ON again
• The OFF time will be the programmed interval - up to approx. 30 seconds
Rear window washing is activated by pressing the wiper stalk switch to the full forward
position.
The washer pump operates followed by two full wiping cycles. The wipers will then
switch to the intermittent wiping mode. Additionally, the system automatically controls the
following safety and convenience features:
• Wiper interrupt with the rear glass opened
• Wiping interrupt with a blocked wiper arm
• Continuous wiping when the vehicle is shifted into reverse 
When the transmission is shifted into reverse, the wiper will switch to continuous operation
until the vehicle is shifted out of reverse. This signal (high) is provided by the LCM III when
it activates the back up lights.
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• If the ignition switch is turned off with the wiper switch in the intermittent position, the rain
sensor will only become active after the ignition is switched back on and one of the fol-
lowing occurs:
- The stalk switch is moved from the intermittent position and then back.
- The knurled wheel setting is adjusted.
- or the wash function is activated.
The reasoning behind this switching strategy is to have the driver make a conscious deci-
sion to activate the system themselves. 
Rain Sensor Control Module Adaptation
The rain sensor control module adapts to the optics system environment as follows:
Windshield Aging:As the vehicle ages the possibility of stone chipping in the rain sensors
monitoring area may occur which will cause a loss of light in the optics system.  
The control module adapts for loss of light based on the intensity of the detected infra red
light with a cleared windshield (wiper motor park signal). Therefore, the rain sensors func-
tion is not adversely affected due to windshield aging.
Dirty  Windows:The  rain  sensor  adaptation  reacts  less  sensitively  to  a  dirty  windshield
(dirt, road salt, wax residue) after a completed wipe cycle. A dirty windshield has a film on
it that diminishes the ability of the infra red to refract into present water droplets. This caus-
es a delay in the rain sensor detection capabilities which lengthens the time intervals on an
intermittent wipe.
Windshield Wiper System Failsafe Operation
The GM provides failsafe operation of the wiper system if faults are detected with any of the
following input signals:
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Central Body Electronics ZKE III
Function Faulted Input Detected Failsafe Function
Intermittent Wipe
Short or open circuit of
the knurled wheel signalDelay value for
setting 3 used.
Intermittent wipe
with Rain SensorFaulted Rain Sensor or 
K-Bus Signal corruptNormal Intermittent
wipe implemented
Wiper Motor not
Functional MovingPark contact feedback
signal takes longer than
16 secondsWiper motor control
deactivated for 3
minutes 

Workshop Hints
Windshield Wiper Blade Service
To access the wiper blades for cleaning or replacement,the following is required:
• With the ignition switched on (KL15), switch the wiper stalk to the “Intermittant” wipe 
mode.
• Switch the ignition off when the wiper arms are in the “upright” position.
CAUTION: Do not allow the wiper arm to spring back against the windshield, glass
breakage will occur!
Rain Sensor Equipped Vehicles
Make sure the wiper blades are in perfect condition. Only use window cleaner to clean the
windows. Dirty  windows  can  cause  the  Rain  Sensor  control  module  to  set  a  fault
due to the end limits of its adaptation abilities.  
Rear Window/Wiper
The  wiper  arm  and  driveshaft  are  connected  by
splines. 
Special  tool  #61  1  320  is  required  to  hold  the  drive
shaft  in  the  park  position  prior  to  installing  the  wiper
arm on to the drive shaft. 
Windshield Wiper System Diagnosis
The GM monitors the following circuits:
• Wiper Potentiometer        • Wiper Motor                           • Terminal 30 
• Double Relay                  • Windshield Washer Pump   
Note: The wiper/washer operation will be interrupted during engine cranking. The GM pro-
vides this “unload” feature to preserve the battery voltage for the starter motor. 
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Central Body Electronics ZKE III
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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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Central Body Electronics ZKE III
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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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Central Body Electronics ZKE III
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E39 Sport Wagon 
Shown
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