Central Body Electronics (ZKE)
Central Body Electronics (ZKE)
ZKE is an acronym for the German words Zentral Karosserie Electronics. Translated to english this is, Central Body Electronics. The ZKE system groups the processing electronics for several body electrical systems into one control module.
The system functions of ZKE control generally include:.
- Central Locking
- Remote Locking - Alarm system
- Power Windows/Sunroof
- Windshield wiping/washing
- Interior lighting
- Electronic power protection
ZKE was introduced on the E32 - 735i in 1988. Since it's introduction several versions of the ZKE system have evolved and are used depending on the vehicle model. The different versions expand on the amount of features provided by the system.
- ZKE = E32 and E34 models
- ZKE II = E31
- ZKE III = E38 and E39
- ZKE IV = E36 Convertibles since introduction (5/94), all other E36's (except Z3 Roadster) after 9-94.
- ZVM = All E36 before 9-94 and Z3 Roadster.
The ZVM system stands for Central Vehicle Module. ZVM is a lesser version of ZKE which was used before ZKE was available for the E36.
The main component of ZKE is the General Module (GM) The GM monitors input signals of the vehicle, processes the information and activates components of the system as shown in the illustration.
All ZKE versions are diagnosable with the DIS tester.
Central Locking
The Central Locking system operates in two stages, Locking and Double locking. The double locking of the doors provides added theft protection by preventing the unlocking of the doors by raising the lock knobs.
The vehicles can be locked or double locked from either front door or the trunk. Early models had two positions for locking on the door lock tumblers. Turning the key to the first position locks and moving past the first position double locks the vehicle. Later models are placed directly into double lock any time the vehicle is locked from the outside.
The vehicle cannot be double locked, by locking, from the inside.
The fuel filler is also locked when the vehicle is locked. A new feature concerning the fuel filler is that it will not lock when the vehicle is locked from the inside.
Driver's door cannot be locked when it is open.
Additional feature of locking is the closing (and on some models) the opening of the windows and sunroof by holding the key in the lock/unlock position.
Remote Locking - Alarm System
Two different remote locking alarm Systems are used. One is the factory installed system that is designated FBZV/DWA. This system is denoted by the remote transmitter being integrated into the key. The system provides most of the features that the key in the lock cylinder will provide plus it arms the alarm system.
This system is installed on the E32 - 740, E34 - 540 and the new E38. The illustration is the system of an E38.
Other vehicles in the model line up with remote locking use an Alpine system. The system ties into the central locking system for the locking functions. This system is installed at the port or in the dealership. This system uses a separate transmitter to carry out the locking/arming commands.
Power Windows And Sunroof
The ZKE control of the power windows and sunroof allows for additional features of window/sunroof operation. This includes the comfort opening and closing with the key. It also allows for toll (or one-touch) operation of the windows and sunroof.
The one-touch feature in the lowering direction is available on most ZKE systems. One-touch in the raising direction requires that the windows be equipped with an anti-trap detection system.
Vehicles that incorporate this anti-trap feature include: E36 coupes, E36 convertibles, 1994 E36 sedans, E31s and E38s.
The sunroofs of the E31, E34 Touring and E38s also have this one-touch feature for operation.
Windshield Wiping/washing
The ZKE control of the wipers allows for additional features such as road speed dependent wiping stages and programming of the intermittent wiping speeds.
The wipers will switch down one speed when the vehicle comes to a stop. For example the slow speed wiping will switch to intermittent when stopped.
The intermittent wiping speed intervals will decrease as road speed increases.
Interior Lighting
The ZKE control of the interior lighting allows various timed operations of the lights.
Interior lights coming on when the door handle is raised.
Interior lights coming on when the key is switched off at night.
Interior lights going off with a delay and/or fade.
Interior lights being switched off after a timed limit if one of the control switches are faulty.
Electronic Power Protection
The ZKE system monitors the current draw on certain components it controls. If the monitored current draw exceeds certain thresholds the ZKE system has has the ability to interrupt the power supply to the components.
The method of interruption is different for the various versions of ZKE as follows:
- ZKE - The GM monitors the current draw of certain components. The components are supplied power through a cutout relay that is controlled by the GM.
If the monitored current draw exceeds the limit, the GM opens the relay removing the power to the components.
- ZKE II - ZKE II functions similarly to ZKE with the addition of a second cutout relay. The second relay allows the power to be supplied by two sources. In the event of a malfunction, the second cutout relay continues to provide power to the balance of the system.
- ZKE III - The GM of ZKE III does not monitor the current draw for the monitored components. A separate Power protection cutout relay module provides the monitoring and control functions. If the current draw exceeds certain limits it automatically opens its contacts like a circuit breaker.
- ZKE IV - ZKE IV only provides power protection for the rear power windows by monitoring the power window motor circuits. If the current draw exceeds a certain limit the relay module will interrupt the power supply to the rear power window motors.