1998 BMW 540i sensor

Principle of Operation
Initialization: Initialization is required for the SHD to learn the end positions of the motor's
travel. The hall sensors provide pulses for motor rotation, the SHD counts the pulses and
determines where the panel is by memorizing the stored pulses.
If the system is not initialized, the sunroof will only operate in the tilt up and slide close posi-
tions. Initialize as follows:
• Press and hold the sunroof switch in either the tilt up or slide close positions for 15 sec-
onds.
• The sunroof motor operates momentarily signifying initialization acceptance.
The SHD memorizes the pulses from the hall sensors on the next activation of the motor
by driving the panel to its end run positions. The SHD senses an amperage increase and
determines the end run position. The counted number of pulses is then used as the basis
for calculating the panel position.
Anti-Trap Feature: The anti-trap feature of the sunroof uses a hall sensor to detect
obstructions while the sunroof is closing (pulse frequency slowed down) in the automatic
close function. The anti-trap feature is shut down prior to full closing (4mm from full closed)
to allow the sunroof to seat into the seal.
Note: The anti-trap feature is not functional when the switch is held in the manual close
position.
Notes: _______________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
49
Central Body Electronics ZKE III

Workshop Hints
SHD Self Diagnosis
The SHD monitors operation and stores fault codes if a defect is determined. The SHD
monitors the following conditions:
• SHD motor relays:The relays are checked for sticking contacts (plausibility) and non
functional contacts.
• Hall effect position sensors:The SHD must detect a pulse frequency from the hall
effect sensor(s) during operation.
• Sunroof Switch: The SHD monitors the signal plausibility of the coded signaling from
the sunroof switch.
Sunroof Fault Response Characteristics
If a fault occurs with any of these functions, the SHD responds as follows:
• Overrides the end run detection.
• Switches the motor off if the relay contacts stick for more than 500 ms.
• Switches the motor off if pulses are not received.
Emergency Operation of the Sunroof
If the sunroof motor does not respond to the switch signals, the hex key in the trunk lid tool
kit is used to manually turn the motor shaft drive.
50
Central Body Electronics ZKE III

System Components
Door Contacts: As mentioned in the Central Locking Section, the existing door contacts
opened/closed are also an input for the interior lighting function. The E53 uses the Hall
effect sensors for the purpose of monitoring door open/closed status (located directly
behind the rotary latch plate encased in the actuator). The sensor is activated by the rotary
latch plate's position.
• Door closed, the rotary latch plate is in the latched position. Current flow through the
hall sensor is < 5 mA.
• Door open, the rotary latch plate is in the open position. Current flow through the hall
sensor is > 12 mA.
A change in current flow informs the General module when a door is opened or closed.
Front Seat Interior/Map Light Unit:The overhead front seat interior light unit contains a
single main interior light. The light is controlled by the GM automatically or by momentarily
pressing interior light switch located on the light assembly.
The switch provides a momentary ground signal that the GM recognizes as a request to
either turn the light on (if off) or turn the light off (if on).
If the switch is held for more than 3 seconds, the
GM interprets the continuous ground signal as a
request to turn the interior light circuit off for the
Workshop Mode
.
The workshop mode is stored in memory and
will not come back on even if the GM is removed
from it's power supply and reconnected. The
switch must be pressed to turn the lights back
on.
There are two reading/map lights also located in the assembly. Each map light is mechan-
ically controlled by depressing the corresponding on/off switch. The power supply for the
map lights is supplied by the GM through the Consumer Cut Off circuit.
53
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.
66
Central Body Electronics ZKE III

67
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

68
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.

Sleep Mode
To lower the constant battery draw when the vehicle is parked, the complete ZKE system
will go into the “Sleep Mode” 16 minutes after the ignition has been switched off and no
further ZKE function is active.
For example, the approximate E39 (528i) Battery draw is:
• Ignition switch off = approx 750 mA.
• One minute after = approx. 560 mA.
• After 16 minutes (sleep mode) = approx. 18 mA.
All modules in the ZKE system will go into the sleep mode. The P-Bus remains active, how-
ever no data transfer takes place until a wake-up request is received. The general module,
door modules or keyless remote module can wake the system up and put the ZKE back
on line. The K-Bus is active (high) in the sleep mode.
Sleep Mode Criteria:
KL R, KL 15 OFF and no further function activated for 16 minutes.
Wake Up Criteria:
KL R or 15 “ON” or a change in one of the signals listed below.
76
Central Body Electronics ZKE III
SIGNAL ACTIVITY ORIGINATING
MODULE
K-BUS High General Module
Door jamb switches (possibility of 4) Low “
Trunk lid lock cylinder microswitch High “
Trunk lid pushbutton microswitch Low “
Interior Trunk lid pushbutton microswitch Low “
Central locking button Low “
Hood microswitch Low “
Trunk Lid microswitch Low “
Interior light switch Low “
FIS sensor Low “
Tilt Alarm sensor Low “
FBZV operational signal High FBZV Module
Driver’s door lock microswitch - (lock) High PM-FT/SB
“ “ “ “ - (unlock) High “
Passenger door lock microswitch - (lock) High PM-BT
“ “ “ “ - (unlock) High “

9. What type of sensor is used to detect the position of a seat with Memory? What type
of signal does it produce?__________________________________________________
_________________________________________________________________________
10. How does the Seat Module communicate a request for a stored memory position with
the mirror modules?_______________________________________________________
________________________________________________________________________
11. On an E38 with Servotronic, why is the speed signal provided to the GM from both
the IKE “A” signal and the K-Bus?___________________________________________
________________________________________________________________________
________________________________________________________________________
12. An E38 customer complains that when exiting the vehicle the steering wheel moves
up. What is the cause of this?______________________________________________
________________________________________________________________________
13. How does the SZM monitor the Seat Heating temperature?_____________________
________________________________________________________________________
________________________________________________________________________
14. What circuits are controlled by Consumer Cut Off? ____________________________
________________________________________________________________________
________________________________________________________________________
15. If a technician double locked a 2000 MY E39 while still inside the vehicle, how could
he/she exit the vehicle?____________________________________________________
________________________________________________________________________
________________________________________________________________________
16. How is the MY 2000 key charged?__________________________________________
________________________________________________________________________
________________________________________________________________________
17. How is the DWA Disarmed (emergency)?_____________________________________
________________________________________________________________________
18. What functions will deactivate the exterior door handle lighting? _________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
80
Central Body Electronics ZKE III