Generic electronics module (GEM)

Generic electronics module (GEM)

The generic electronic module is installed on the passenger's side underneath the dash panel.

It replaces separate components such as the central locking module, the timer relay and the fuse box in the passenger compartment.

It consists of a power distribution section (including fuses and relays) and an electronic control module, which controls the operation of most of the electronic convenience systems.

New vehicles are supplied with different versions of the GEM (depending on the equipment specification of the vehicle). Only one version is available for service repair work. When installing a replacement GEM it needs to be configured for the specific vehicle.

The following functions are controlled or executed by the GEM if the battery voltage is between 9 and 16 V.
• Battery saving function
• Current distribution
• Exterior lighting (except the adaptive front lighting function on vehicles with dynamic cornering lights)
• Interior lighting
• Wiper system
• Washer fluid level indicator
• Window heating (heated windshield, heated rear window, heated exterior mirrors)
• Speed control system (reads the speed control switches and transmits signals on the CAN bus)
• Locking / Unlocking
• Anti-theft
• Air conditioning controls (partial)
• Handbrake (it monitors the switch and transmits the signal on the CAN bus)
• Monitoring of the brake fluid level.
• Fuel pump (vehicles with 1.6L, 2.0L and 2.3L engine)
• Fuel level indicator
• Battery charging (smart charge, partially)
• Electric booster heater
• Detection of the accelerator pedal position (APP) sensor
• Detection of the clutch pedal switch
• Detection of the clutch pedal position (CPP sensor)
• Brake pedal position (BPP) switch.
• Tire pressure monitoring system
• Communications via the high speed CAN bus (HS-CAN) and mid-speed CAN bus (MS-CAN)
• Main module in the LIN bus system
• PATS (interface for transceiver)
• Clock control

The GEM can be diagnosed via the diagnostic tool. Furthermore, an integrated service mode enables testing of the input and output signals without the need for further tools.
For additional information, refer to: Generic Electronic Module (GEM) (419-10 Multifunction Electronic Modules, Diagnosis and Testing).

Emergency function

The GEM is equipped with restricted emergency running functions on vehicles with medium or high levels of equipment.

A monitoring function within the GEM is sent a control signal at regular intervals by the microcontroller. If for example the battery voltage drops below a voltage of approx. 7.5 Volt then the control signal is not sent and the GEM goes into emergency running mode after a specified time.

In this case the dipped beam headlamps and the side lights are switched on permanently depending on the position of the light switch.

In the event of a communication fault between the wiper switch and the GEM the wiper system performs continuous wiping at normal wipe speed regardless of the wiper switch position. The emergency running mode is switched off when the ignition switch is turned to "0".

Light switch

The light switch has been modified and now includes electronic controls. It is connected to the GEM via a control module subnetwork (LIN) bus.

If the ignition lock is in position "0" for more than 3 minutes then the front fog lamps, rear fog lamp and the main beam headlamps are deactivated if they were previously activated.