Body Control Systems: Description and Operation

Front Electronic Module

Front Electronic Module (FEM)
The Front Electronic Module (FEM) represents a new generation which supersedes existing control units and their functions. As a result of the modular principle, the Front Electronic Module (FEM) can be installed in all series. The Front Electronic Module (FEM) is the central control unit in the vehicle electrical system. At the same time, the Front Electronic Module (FEM) is the gateway for the other control units. The Front Electronic Module (FEM) provides functions from the previous control units footwell module (FRM), Car Access System (CAS), Junction Box Electronics (JBE) and central gateway module (ZGM). The central gateway module (ZGM) is installed in the Front Electronic Module (FEM) as an independent control unit. The aim is to reduce the number of control units and improve component networking. At the same time, the optimization of the wiring harness reduces the physical bus capacity.

Functional description
The following functions of the Car Access System (CAS) have been integrated in the Front Electronic Module (FEM).
- Terminal control
- Electronic immobilizer
- Comfort access system
- Electric steering lock
- Central locking system

The following functions of the Junction Box Electronics (JBE) have been integrated in the Front Electronic Module (FEM).
- Power window regulator
- Wash/wipe system
- Washer jet heating
- Climate control
- Seat heating
- Mirror heating
- Automatic air recirculation control (AUC)
- Rain-light-solar-condensation sensor

The following functions of the footwell module (FRM) have been integrated in the Front Electronic Module (FEM).
- Exterior lighting
- Brake lamp
- Interior lighting
- Exterior mirrors

The central gateway module (ZGM) is integrated in the Front Electronic Module (FEM). It is seen as a control unit within the control unit, as the central gateway module (ZGM) acts as a self-sufficient control unit within the Front Electronic Module (FEM).
The task of the central gateway module (ZGM) is to connect all bus systems. This combination allows general use of information from the individual bus systems. The central gateway module (ZGM) is able to implement various reports and speeds on other bus systems. The programming data are transferred to the vehicle by Ethernet via the central gateway module (ZGM).
The Front Electronic Module (FEM) is located in the A-pillar of the passenger footwell and controls all functions in the front section of the vehicle.







Structure and inner electrical connection
The front electronic module (FEM) is connected to the vehicle with 9 plug connections.
To avoid confusion during connection, connector housings of the same colour have different encoding. This prevents them being inserted in the wrong position inadvertently.
The input for the voltage supply of the FEM is a 1-pin plug connection.
Fuses for the following consumer units are installed in the fuse block of the Front Electronic Module (FEM):
- Central locking drive
- Outside door handle electronics
- Powertrain of the power window regulators
- Light operating facility, operating facility for the assist systems and steering column switch cluster
- Rear Electronic Module (REM) and headlight driver module
- Fanfare







Pin assignments
The graphic above shows only the supply and bus connection. The current pin assignment is recorded on the wiring diagrams in the ISTA diagnosis system (Integrated Service Technical Application). Click on the component code in the wiring diagram to activate the "Installation location" and "Pin assignment" tabs.

Nominal values

Observe the following setpoint values for the front electronic module (FEM):

Size Value
Supply voltage 9 to 16 volts
Temperature range -40 to 80 °C

Diagnosis instructions

Failure of the component
In the event of a communication malfunction to the front electronic module (FEM), carry out the standard checks (global procedure). If there is an internal control unit fault, the following behavior is to be expected:
- Fault code entry in the front electronic module (FEM)

We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.