BMW 525I 1998 E39 Central Body Electronics ZKE Manual

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Central Body Electronics ZKE III
System Components: Inputs - Processing - Outputs
645200136.eps

Driver’s Seat (E38/E39)
Principle of Operation
Each motor for seat adjustment contains a micro-processor (called a Ripple Counter) that
receives a digital signal from the seat control module for motor activation. The motors are
connected to KL 30 and KL 31 and respond to the signals generated by the seat module
when seat movement is requested. The seat adjustment switch provides ground input sig-
nals to the module when seat movement is desired. The module processes these input sig-
nals and sends output signals to the seat motor processors. The seat motor processors
activate the motors and the seat moves to the desired point.
The circuitry of the Ripple Counter detects the motor activation current. As the armature
segments of the motor rotate passed the brushes, the current flow rises and falls produc-
ing a ripple effect. The peaks of these ripples are counted and stored in the Ripple Counter
module. The memory function of the seat module uses this ripple count instead of feed-
back potentiometers to memorize and recall seat positions.
Ripple Count Recognition:
When the seat is installed and the
battery is connected, the ripple
counter uses the initial position of
the motors as the “Zero Position”.
Any movement from this point is
counted as “+” or “-” pulses as
the motors move in either direc-
tion.
The pulse position of the motors is stored in the seat module, in an EEPROM (of the PM-
SM), before the ZKE goes into its “Sleep Mode”.
This prevents the position recognition from being lost. If the battery is disconnected before
the 16 minute sleep mode activation, the memory positions of the seat will be lost and
reprogramming will be required.
Diagnosis: The PM-SM communicates with the DISplus or MoDiC. The PM-SM monitors
the seat motors and circuits as well as it's internal operation. Any detected faults are stored
in the PM-SM fault memory and are called up when diagnosing the system with the Fault
Symptom diagnostic plan. The PM-SM also provides status display to the DISplus of the
input and output control signals as well as component activation.
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Central Body Electronics ZKE III
615200137.eps

Passenger’s Seat (without memory)
Principle of Operation
The passenger seat control switch is purely a mechanical switching module that activates
the passenger seat motors without position monitoring capabilities. Due to the limited op-
eration requirements, the passenger seat control switch is not equipped with on board
diagnostics.
The Passenger Seat control switch is equipped with an overload protection function. If
excessive amperage is drawn due to a defective motor or a switch is stuck driving a motor
to the end limit, the function activates opening the motor control circuit.
Passenger Seat Motors: Each motor is individually controlled by the Seat Control Switch.
Each position motor is connected to the seat position switch by a two wire circuit provid-
ing motor activation in both directions (no position recognition).
Passenger Seat Adjustment: Operation of the passenger seat is always possible regard-
less of the ignition key position. Moving a position switch operates a the motor control con-
tacts directly, the switch applies voltage and ground path directly to operate the motor.
Reversing the switch simply changes the motor polarity. More than one passenger seat
motor can be run simultaneously.
Optional Seat Back Lumbar Support
The optional air bladder lumbar support system is similar in all
vehicles (if equipped). Each seat contains the following com-
ponents:
• Four position circular rocker switch in the seat base trim in
the area of the seat switches.
• Electrically controlled air compressor with over pressure cut
out under each seat.
• Two solenoid activated air controlling valve blocks (one per
air bladder). Each valve block includes an inlet and an outlet
valve. When energized they direct air into the bladder(s) to
inflate or relieve trapped air to deflate the bladders.
• Connecting hoses and air bladders in lower seat back.
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Central Body Electronics ZKE III

Principle of Operation
The lumbar support system can be operated at any time regardless of key position. The
four position circular rocker switch provides power switching to operate the system as fol-
lows:
• Position 1: The internal switch contacts provide a power and ground path for both valve
block inlet valves and the air compressor. Both bladders inflate until the switch is
released. If the switch is held continuously, an overpressure bypass valve opens on the
compressor preventing damage to the bladders.
• Position 2: Compressor activated, upper bladder inflates, lower bladder deflates.
• Position 3: Compressor activated, lower bladder inflates, upper bladder deflates.
• Position 4: Compressor is not activated. Upper and Lower bladders both deflate.
This function is not stored in memory for recall.
Diagnosis
The seat lumbar support system is purely electro-pneumatic control system. No electron-
ic diagnostic communication is possible.
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Central Body Electronics ZKE III

Comfort Seats (standard on E38 750iL, other models if equipped)
This option provides additional back support in the
shoulder area. An additional adjustment in the upper
backrest allows forward “contour” that is controlled by
a rocker switch in the side panel.
When the ignition is on or off, the two way rocker switch
can be pushed until the desired setting is achieved (for-
ward/backward tilt). The motor drive operates the same
as the seat motors.
The shoulder support adjustment is also stored in
memory for recall.
Active Seat (E38 - if equipped)
Purpose of the System
Actively changing the surface of the seat helps to prevent muscle tension and fatigue par-
ticularly on long trips or sitting in one position for a long period of time. The seat causes
weight transfers which are slight and imperceptible enhancing driving comfort. The basic
seating position is not changed by this.
In the seat’s upholstery beneath the surface of the seat is a cushion of fluid on the left and
right. The fluid is slowly circulated back and forth between the cushions by a pump.
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Central Body Electronics ZKE III

Principle of Operation
To activate this feature, the ignition must be in
the KL R or KL 15 and press the switch located
in the Center Console Switch Center (driver and/
or passenger front seat).
The switch provides a ground to the control
module and an LED in the switch will illuminate.
If there is a fault in the system the LED will not
illuminate.
The control module, fluid bladders (2 and 3) and
pump (1) is contained in each seat. The pump
contains a Hall sensor to monitor the number
motor revolutions and two pressure sensors to
monitor each bladder for vacuum (indicating
empty).
The fluid bladders (2 per seat) contain water-
glysantin mixture and are connected to the fluid
pump. The fluid bladders are equal in volume at
rest (15 mm. high) and will raise from 0 up 30
mm. when filled alternately from left to right.
Note: The pump unit and fluid bladders are replaced as a unit.
The control modules (one per seat) are connected to the P-Bus. The driver’s side control
module contains an acceleration sensor that monitors transverse acceleration of the vehi-
cle. Active Seat operation is temporarily interrupted during high acceleration.
Rear Power Seat (E38 750iL)
The rear seats in the 750iL provide electric adjustments for:
1. Backrest Angle - Control switch powers the motor.
2. Headrest Height - Control module behind each upper seat.
3. Lumbar Support
The headrest automatically extends when a passenger fastens
the safety belt and will automatically retract when the safety
belt is released. The power rear seat is a purely electric control
system. No electronic diagnostic communication is possible.
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Central Body Electronics ZKE III
Seat Heating Operation (from 99 MY)
Principle of Operation
The front seat heaters are adjustable through three ranges of
heating output temperature.
Pressing the respective seat heater button once provides
stage 1:
• All three LEDs illuminate and the heating elements are provided regulated output current
producing a seat temperature of 111
OF.
Pressing the button a second time provides stage 2:
• The top LED switches off and the heating elements are regulated to an output tempera-
ture of 102
OF.
Pressing the button a third time provides stage 3.
• The top and middle LEDs are off and the heating elements are regulated to an output tem-
perature of 95
OF.
The SZM monitors the seat heating element temperature via an NTC feedback signal to
regulate the output current which maintains the seat temperature.
Seat heating is switched off by pressing the button a fourth time,
pressing and holding the
button for more than 1 second or when the ignition is switched off.
System Components
Carbon Fiber Heating Pads:In each seat is a two
section heating pad wired in parallel. The heating pads
are resistors which when powered produce radiant
heat.
The seat base heating element also contains a temper-
ature sensor for feedback to provide the temperature
regulation output control.
KL31
KL15
TEMPERATURE
SENSOR
615200139.eps

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Central Body Electronics ZKE III
Center Console Switch Center (SZM): From 1999 MY E38, E39 and E53 vehicles are
equipped with a SZM to control the front seat heating and provide a diagnostic interface
with the DISplus/MoDiC via the K BUS.
The SZM directly controls:
• Front Seat Heating
• Rear Window Roller Blind
SZM also provides a unitized switching center
for:
• Park Distance Control (PDC)
• Dynamic Stability Control (DSC III)
• Electronic Damper Control (EDC).
The switch signal output for these systems is a direct output signal. All diagnosis functions
are carried out through their respective control systems.
SZM Monitoring of Seat Heating
Battery Voltage:The SZM switches current supply to the heating elements off when bat-
tery voltage drops below 11.4 volts. However, the heating stage LEDs remain on.
Regulated output current resumes when battery voltage raises above 12.2 volts for more
than 5 seconds.
SZM Internal Temperature: The power output stages for the seat heating elements gen-
erate a considerable amount of heat when in stage 1 operation. The SZM monitors it’s own
internal temperatures and reduces the heating output when internal temperatures rise to a
temperature of 185
OF or switches it off completely above 203OF. As with battery voltage
monitoring, the heating stage LEDs remain on when these temperatures are exceeded.
Fault Monitoring:The SZM monitors the temperature sensors and heating mats for faults.
Detected faults are stored in the SZM. Fault Symptom Troubleshooting in conjunction with
stored faults will initiate the diagnostic paths using the DISplus/MoDiC. The following faults
can be recognized:
• Shorts or opens in the wiring circuits.
• Shorts or opens in the temperature sensors.
• Open in heating element.
If a short is detected in the temperature sensor, the seat heating is switched off to prevent
overheating. The Stage LEDs are also switched off with this fault present.

Rear Window Roller Sunblind Operation
The roller sunblind is activated by momentarily pressing and releasing (one touch) the sun-
blind rocker switch in the SZM. The SZM activates the motor in the appropriate direction.
The SZM switches the motor off when the motor amperage increases indicating the blind
has reached the end of its intended travel.
Fault Monitoring: The SZM continually monitors the motor drive amperage loads to deter-
mine jamming or blockages. If current values exceed preset values, the motor is switched
off immediately.
Faults are stored in the SZM for opens or shorts in the motor or motor’s wiring circuit. The
SZM also provides diagnostic requests to monitor the switch input status via the DISplus/
MoDiC.
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Central Body Electronics ZKE III
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KL 30 (BATTERY)KL 30 (BATTERY)-+
KL 15 (IGNITION ON)KL 15 (IGNITION ON)
KLR (ACC)KLR (ACC)
KL 87 (OPERATING POWER)KL 87 (OPERATING POWER)
58G (PANEL LIGHTING)58G (PANEL LIGHTING)
LCM IIILCM III
PDC
EDC
DSC
MREAR WINDOW
ROLLER
BLINDSREAR WINDOW
ROLLER
BLINDS
DRIVER’S SEAT HEATINGDRIVER’S SEAT HEATING
PASSENGER’S SEAT HEATINGPASSENGER’S SEAT HEATING
K BUSK BUS
PDC CONTROL
MODULEPDC CONTROL
MODULE
EDC CONTROL
MODULEEDC CONTROL
MODULE
SZMSZM
DSC III
CONTROL
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CONTROL
MODULE
ACTIVE SEAT
CONTROL
MODULESACTIVE SEAT
CONTROL
MODULES
System Components: Inputs - Processing - Outputs

Steering Column
Principle of Operation
The electrically adjustable steering column used in the various
models (if equipped) is similar in components, mechanical link-
ages and electrical operation.
The steering column adjusting switch is mounted on the left
side of the steering column and provides for four directions of
column movement. The steering column switch inputs are
processed by the seat module.
Motor Drives:
Forward/Back (Telescope)
A flexible drive shaft operates a
screw drive which causes a for-
ward/back movement of the stee-
ring column.
Up/Down
A flexible drive shaft moves an off-
center lever causing up/down
steering movement.
The motors for tilt and length also employ ripple
counter modules for motor control and memory
recall.
The control electronics for the steering column
are integrated into the seat module.
The output signals are sent from the seat mod-
ule to the steering column ripple counter mod-
ules for motor activation.
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Central Body Electronics ZKE III