Central Body Electronics (Zke Iii) - Overview - E38, E39 & E53: Overview BMW 5 series E39 facelift

Model: E38, E39 and E53

Production: From Start of Production

The ZKE III system was introduced on the E38 in 1995 and subsequently used on the E39 and the E53. ZKE III is responsible for the control of various body electronics systems. Although there are some functional differences from model to model, the majority of the functions and systems are identical.

The ZKE III system is comprised of the General Module (GM III) which is connected to a network of peripheral modules all connected by a bus network. The Peripheral Bus (P-Bus) is responsible for transferring commands and information between various system components.

The modules on the P-Bus which are connected to the GM include

Scheme 405

1. Driver's side door module (switchblock) PM-FT/SB
2. Passenger door module (PM-BT)
3. Sunroof module (SHD)
4. Seat/mirror/steering column module PM-SM

The modules of the ZKE III system are networked together by the P-Bus to control the functions of the body electronics which include

Systems controlled directly by the GM III

1. Windshield Wiping/Washing
2. Automatic Interval Control (Rain Sensor)
3. Headlight Washing
4. Tailgate Wiping/Washing
5. Interior Lighting
6. Central Locking
7. Keyless Entry
8. Key Memory
9. Power Trunk Release
10. Electric Opening of Tailgate
11. DWA Alarm System
12. Servotronics
13. Consumer Cut-off/sleep mode
14. Diagnosis

Systems controlled by the Driver's Door Switch Block module

1. Power Windows
2. Mirror Adjustment/Memory/Heating

Systems controlled by the Passenger's Door Module

1. Mirror Adjustment/Memory/Heating
2. Power Windows

Systems controlled by the Sunroof Module (SHD)

1. Power Sunroof

Systems controlled by the Seat/Mirror/ Steering Column Memory Module

1. Seat Adjustment/Memory
2. Steering Column Adjustment/Memory

Principle Of Operation

The optical infra red portion of the sensor operates by the principle of refraction (bending of a light ray). The rain sensor control module activates the emitter diode which sends a beam of infra red light through the windshield on an angle. The set angle is important because it provides the beam with a calculated reflective path back to the detector diode.

The beam is reflected back into the windshield due to the density difference of the glass compared with the ambient air on the outside surface of the glass. When the windshield is clean (no rain drops, moisture or dirt) the detector diode receives 100% of the infra red light that the was sent by the emitter. With this condition, the rain sensor evaluation electronics determines the windshield is free of rain drops.

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The density of water is closer to that of glass than air. When rain starts to accumulate in the sensor monitoring area, it causes part of the infra red beam to extend past the outside surface of the glass and into the rain drop. When this occurs, the beam is refracted and only part of the beam returns to the detector diode.

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The rain sensor evaluation electronics determines the windshield has a few rain drops (or dirt) on it. The intensity of the returned infra red beam diminishes proportionally with an increase of water droplets. The rain sensor control module generates a signal proportionate to the amount of rain on the windshield and broadcasts it to the GM via the K bus.

The GM activates the intermittent wipe cycle if the windshield wiper stalk switch is in the intermittent position. It also adjusts the frequency of wiping the windshield depending on the four position thumb wheel.

Windshield Wiper System Fail-Safe Operation

The GM provides fail-Safe operation of the wiper system if faults are detected with any of the following input signals

FUNCTION SPECIFICATION

Panic Mode Operation

When the trunk button is pressed and held, the GM is signaled to activate the siren for the Panic Mode. The panic mode is function with either an armed or disarmed DWA system.

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.

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The interior light switch is a push button switch that will carry out the opposite command of the current status of the lights. (ie: if the interior lights are currently on, pushing the button will switch the lights off.)

1. If the interior lights are switched "ON" by the button with the ignition switched ON, the interior lights will remain on until they are switched off by the button.
2. If the interior lights are switched "ON" when the ignition is switched OFF, the lights will remain on for 16 minutes (consumer cutout).
3. Pressing the interior light button for longer than three seconds will switch the lights to continuous off. This feature is intended for workshop use. Pressing the button again will return the lights to the normal operational status.
4. Locking the vehicle from the outside will immediately switch off the interior lights.

The ON/OFF conditions for the interior lights in the automatic mode are as follows

Lights ON: The exterior visual entry aid lighting is activated "on" when the vehicle interior lights are activated "on" automatically by the GM.

Lights OFF: Immediately after KL 15 recognition (immediate off - no soft off function). Soft off after a short delay once all doors are closed.

After a maximum of 20 seconds "on" time, the control module switches exterior visual entry aid lighting off regardless of interior light status.

Mirror Operation

The output stages and memory storage of mirror positions is handled by the respective door modules. The positioning of the mirrors is signaled from the driver's door switch block/module. The signal passes over the P-Bus to the passenger's door module.

The memory/recall for the driver's mirror comes directly into the door module from the memory switch. The operation for the passenger's side mirror is carried out over the P-Bus from the driver's door module to the passenger's door module.

The memory positions are stored in each respective module. The memory position is recognized by the feedback potentiometers located on each mirror motor.

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The reverse gear tilt feature for the passenger's mirror is signaled from the GM, over the P-Bus, when reverse is selected and the mirror switch is set for the driver's side.

Mirror heating is controlled by each respective door module. The GM receives the outside temperature from the IKE and passes it to the door modules. The "ON" time for mirror heating is adjusted based on the outside temperature.

A pulsed heating cycle is used for the mirrors based on the outside temperature.

TEMPERATURE SPECIFICATION

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The lumbar support system can be operated at anytime regardless of key position. The four position circular rocker switch provides power switching to operate the system as follows

1. 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.
2. Position 2: Compressor activated, upper bladder inflates, lower bladder deflates.
3. Position 3: Compressor activated, lower bladder inflates, upper bladder deflates.
4. Position 4: Compressor is not activated. Upper and Lower bladders both deflate.

This function is not stored in memory for recall.

Scheme 411

The electrically adjustable steering column used in the various models (if equipped) is similar in components, mechanical linkages 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.

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To activate this feature, the ignition must be in the KL R or KL 15 and press the switch which is 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.

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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.

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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 vehicle.

Active Seat operation is temporarily interrupted during high acceleration.

The front seat heaters are adjustable through three ranges of heating output temperature.

Pressing the respective seat heater button once provides stage 1

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1. All three LEDs illuminate and the heating elements are provided regulated output current producing a seat temperature of 111°F.

Pressing the button a second time provides stage 2

1. The top LED switches off and the heating elements are regulated to an output temperature of 102°F.

Pressing the button a third time provides stage 3.

1. The top and middle LEDs are off and the heating elements are regulated to an output temperature of 95°F.

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.

Rear Window Roller Sunblind Operation

The roller sunblind is activated by momentarily pressing and releasing (one touch) the sunblind 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 determine 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/GT-1.

Control logic (example E38) includes

1. Servotronic control electronics active with KL R being switched "ON" - ensure no delay in operation if engine is started and vehicle is immediately driven.
2. Plausibility check for speed signal - the control electronics monitor both the Speed signal "A" from the IKE and the vehicle speed signal on the K-Bus.
3. The ability to detect both acceleration and deceleration from the two speed signals - the speed signal from the IKE is updated every two seconds.
4. The servotronic assist is reduced gradually when the vehicle is under acceleration.
5. The servotronic assist is adopted to the lower direct reading during decel or braking.

Electric/electronic failures with the servotronic system will result in the following

1. Power/electronic failure of the control module or solenoid - steering assist the same as high speed driving (increased effort).
2. Vehicle speed signal missing - control module retains the assist mode in effect when the speed signal was lost.
3. Speed signal implausible - steering assist the same as high speed driving (increased effort).

The GM also provides the diagnostic "gateway" to the Servotronic status and "Component Activation" via the DISplus/GT-1.