System Components

General Module (GM IV):  The GM is a microcomputer that is the central component (heart) of the Central Body Electronics. The GM is located behind the glove box.

The main objectives for using the GM are:

• Increase Overall Reliability.
• Centralize Electronic Systems.
• Decrease Assembly and Service Repairs.
• Centralized Diagnosis of all ZKE Components.
• Individualization of Features (Coding).

Fig 1: Identifying General Module (GM IV)

Courtesy of BMW OF NORTH AMERICA, INC.

The GM requires input  data to perform Central Body Electronics functions. The inputs are supplied by digital switched signals such as:

• Driver's Door Lock Microswitch:  supplies voltage (KL 30) to the GM when switched. A path to ground is provided by the GM (internally). The GM monitors the input voltage.
• Central Lock Button (E36 from 96 MY):  supplies a ground circuit to the GM when switched. The GM supplies and monitors a reference voltage (5v) that is "pulled" low when the switched ground path is provided.
  Fig 2: View Of Driver's Door Lock Microswitch Circuit Diagram

  Courtesy of BMW OF NORTH AMERICA, INC.

The GM processes  the input information and contains "coded" instructions that allow a specific output control of functions.

The GM will produce output  controls using internal transistors to switch relays allowing current flow (providing voltage or ground) through circuits and actuators. Actuators ( such as relays and motors) are used by the GM to operate or control various output functions.

Fig 3: Identifying Fuel Filter Flap Motor Circuit Diagram

Courtesy of BMW OF NORTH AMERICA, INC.