The GEM is an independent control module which controls a series of functions of the body electrics.
It replaces various previously used components, such as the turn signal relay, the Central Timer Module (CTM) and the central locking module.
The GEM is an independent control module which controls a series of functions of the body electrics.
The headlamp switch-off delay utilizes the low beam together with the peripheral lights (if equipped) to illuminate the area surrounding the vehicle. The function is activated by turning the light switch to the "headlamps" position with the ignition switch in the "0" position.
On vehicles with "autolamps", the function is activated by turning the light switch to the "Auto" position with the ignition switch in the "0" position.
After the last door has been closed, the function remains active for a further 30 seconds and then switches off automatically.
When a door or the liftgate is open, the switch-off time is extended to 180 seconds. After the last door has been closed, the switch-off time is reset to 30 seconds.
The headlamp switch-off delay can be deactivated by operating the high beam switch again or by switching on the ignition prematurely.
The lamps used for the peripheral lights are the front side lamps, rear lamps and license plate lamps.
The combined rain sensor/light sensor is attached to the windshield, near the interior rear view mirror.
The ambient light sensor determines the general light intensity. For this purpose, it detects the light over as wide an angle as possible, without taking the direction of incidence into account.
The front light sensor determines the light intensity directly in front of the vehicle.
If both the ambient light sensor and the front light sensor detect a sudden reduction in light intensity at the same time, then an algorithm-based calculation is used to determine the fact that the vehicle has entered a tunnel, a multi-storey car park or a long underpass.
In this case the request for switching on the external lighting and the indicator in the instrument cluster is transmitted to the GEM.
If the vehicle enters into the shade thrown by a large truck, the two sensors will register different light intensities. In this case, the algorithm-based calculation will not result in the lights being switched on.
Turn signals
The GEM actuates the turn signal lamps for direction indication and the hazard flasher. It therefore replaces the conventional turn signal relay.
For the turn signal, the turn signal lamps at the front, rear and on the side of the vehicle, as well as the indicator in the instrument cluster are activated according to the position of the turn signal switch at approx. 80 impulses per minute.
An audible sound is generated with the same rhythm by a sound generator in the instrument cluster as an audible check for the driver.
If one of the turn signal lamp bulbs fails then the flashing frequency is increased to around 160 impulses per minute. On vehicles with message center in the instrument cluster, a message is generated.
As these signals could overlap in certain situations, a priority level has been assigned to each one.
- Priority 1: hazard signal
- Priority 2: alarm triggered
- Priority 3: turn signal
- Priority 4: confirmation of locking/activation of alarm
- Priority 5: confirmation of reprogramming
Lane-change flasher - vehicles built from 08/2005
With the lane-change flasher, the turn signals flash in a three-flash mode. For this purpose, the turn signal lamp switch is turned to the first non-engaged position and released again within 0.1 to 0.7 seconds. If the turn signal lamp switch is held in this first position for less than 0.1 seconds or longer than 0.7 seconds, the turn signal system responds in single-flash mode for as long as the turn signal switch is held or remains in the engaged position. The three-flash mode can be configured via Worldwide Diagnostic System (WDS) or the instrument cluster personalization menu.
Interior lighting
Depending on the model and the equipment level of the vehicle, the interior lighting controlled by the GEM includes the overhead light at the front and rear and the luggage compartment light.
The overhead lamps are only switched by the GEM if the corresponding lamp has been set to "Door operation" (not if the light is in the "Continuous" or "Off" settings).
NOTE:On vehicles built up to 08/2005 with Ax GEM, there are no switches in the locks of the rear doors. As a result the overhead lights are not switched on when the rear doors are opened.
NOTE:On vehicles built from 08/2005 with Ax GEM and manual locking/unlocking with a key, there are no switches in the locks of the rear doors. Vehicles with central locking/unlocking with remote radio control are equipped with switches in the locks of the rear doors.
The lights are switched off when all the doors and the liftgate are closed and one of the following conditions is satisfied:
- 25 seconds after the lights are switched on or after closing the last door on non centrally locked vehicles
- On closing the last door on centrally locked vehicles
- The ignition lock is turned from position "0" or "I" to position "II"
- Ignition lock in position "0" or "I" while the vehicle is being locked
On vehicles built up to 08/2005, dimming is used when switching on and off in the case of the Cx and Dx GEM versions.
On vehicles built from 08/2005, dimming is used when switching on and off in the case of the Ax, Bx, Cx and Dx GEM versions.
When the lights are switched on, their operating voltage is brought from 0V to operating voltage within a period of 0.7 seconds.
When the lights are switched off, the operating voltage is continuously reduced to 0V within a period of 1.7 seconds.
The dimmer function is not utilised if the lights are switched off by the battery protection function.
Heated windshield
The heated windshield can only be switched on if the engine is running.
The GEM switches on the relay for the heated windshield in response to a request from the switch in the instrument panel.
On vehicles built from 08/2005, the GEM also switches on the relay for the heated windshield in response to a request from the "Max Defrost" button on the Electronic Automatic Temperature Control (EATC) climate control assembly.
The Light Emitting Diode (LED) in the corresponding switch lights up continuously while the windshield is being heated.
Rear window heating
The rear window heating can only be switched on with the ignition key in position "II".
The GEM switches on the relay for the heated rear window in response to a request from the switch in the instrument panel.
On vehicles built from 08/2005, the GEM also switches on the relay for the heated rear window in response to a request from the "Max Defrost" button on the EATC climate control assembly.
The LED in the switch lights up continuously while the rear window is being heated.
NOTE:If the vehicle is equipped with heated exterior mirrors, then these are operated together with the rear window heating.
Windshield wash/wipe functions
NOTE:All the wash/wipe functions are only available if the ignition key is in position "II".
The windshield wiper switch has four settings: Off, Intermittent, Level 1 and Level 2.
On vehicles built from 08/2005 with rain sensor, the wiper switch also features an Auto function.
In levels 1 and 2 the wipers run continuously at normal or high speed.
In the intermittent setting a wipe is performed every 7 seconds when the basic setting is selected.
On vehicles built up to 08/2005, the interval is continuously adjustable. For this purpose, the wiper switch is set to the intermittent wipe position and then switched back off after the first wipe. After the desired wipe interval has elapsed the switch is again moved to the intermittent wipe position. The intermittent wipe delay time is then stored in the GEM.
The time delay can be adjusted to between 1 and 25 seconds.
When the ignition is switched off the time delay is reset to the basic setting.
On vehicles built from 08/2005, the intermittent mode can be adjusted in 6 stages via a rotary switch on the wiper lever.
Windshield wash/wipe function
If the washer switch has been activated with the wiper switch in the "Off" position, the washer pump is switched on first to protect the wiper blades, and then after a short delay the wipers. The wipers then perform 2 or 3 wipes.
The after-wipe function on the windshield ensures that any water remaining on the windshield after washing is wiped away. It is only required if the wipers are switched off or set to intermittent mode.
If the wiper switch is in the "Off" position then an after-wipe operation is performed 4 seconds after the washing process is finished.
When the wipers are in intermittent mode the after-wipe is performed after 6 seconds, but only if the wiper delay time is set to more than 6 seconds. Afterwards the wipers continue in intermittent mode.
If the wipers are in operation at normal or high speed when the washer is activated then they continue to run at this speed.
Automatic windshield wipers - vehicles built from 08/2005
The rain sensor and the light sensor are integrated into one housing.
The rain sensor consists of an opto-electronic measuring and evaluation circuit. The sensor calculates the amount of precipitation falling on the windshield and request that the windshield wipers are switched on.
On the basis of the information provided by the rain sensor, the windshield wipers are then automatically set to the required wipe speed.
Rain sensor operating principle - vehicles built from 08/2005
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Installation position of the combined rain/light sensor
Rear window wash/wipe function
The rear window wiper changes the wiper delay interval according to the setting of the windshield wiper switch.
If the windshield wiper switch is set to Level 2 and the rear window wiper is switched on, then the wiper delay interval is 6 seconds.
If the windshield wiper switch is in the Intermittent or Level 1 position and the rear window wiper is switched on, the wiper delay interval is 10 seconds.
If reverse gear is engaged while the windshield wiper is switched on and the rear window wiper is switched off, then the GEM automatically switches on the rear wiper with the wiper delay interval as described above. This function remains activated until reverse gear is no longer engaged or the windshield wiper is switched off.
Rear window wash/wipe function
When the switch for the rear window washer is activated the wipers perform wipe operations (while the switch is being activated).
When the switch is released the wipers perform 2-3 more wipes.
Information/warning functions
A warning lamp in the instrument cluster is actuated if at least one door or the liftgate is not fully closed with the ignition lock in position "II".
NOTE:On vehicles built from 08/2005, a message is transmitted to the instrument cluster by the GEM via the medium-speed Controller Area Network (CAN) bus in order to generate an acoustic signal.
Message center - vehicles built from 08/2005
Depending on the various model versions, different information is transmitted by the GEM to the message center integrated in the instrument cluster via the medium-speed CAN bus.
The various information can be displayed by pressing a button on the turn signal lamp switch.
WARNING:For reasons of safety, modification of the various functions should only be performed when the vehicle is stationary.
Various functions which are monitored and controlled by the GEM can be modified by means of the button on the turn signal lamp switch.
Modifiable functions
- Confirmation tone (all/minimal)
- Vehicle remote keyless entry (all doors/only driver door)
- Lane-change flasher (3x flashing/1x flashing)
- Hazard flasher during sharp braking (activated/deactivated (only for certain markets))
Locking/unlocking - central locking
Locking/unlocking - central locking
The central locking system locks all doors and the liftgate so that they can no longer be opened from the outside.
The central locking system is activated by turning a key in one of the door lock cylinders to the locking position.
The central locking can also be activated by pressing the internal door openers into the locking position.
If during the central locking process one of the front doors is not fully closed then all the doors are unlocked again.
If during the central locking process one of the rear doors is not fully closed then all the doors are still centrally locked.
Locking/unlocking - double locking
The double locking system locks all doors in such a way that they can neither be opened from the outside nor the inside of the vehicle.
The double locking mechanism is only available if the ignition lock is in the position "0" or "I" and the front doors are fully closed.
To activate the double locking, press the locking button on the radio remote control twice within 3 seconds, or insert the key into one of the door locks and turn it first to the unlocking position and then within 3 seconds to the locking position.
All the turn signal lamps flash twice to confirm activation of the double locking.
If the ignition lock is in the position "II" or one of the rear doors is not fully closed then the vehicle is centrally locked but not double locked.
If within 45 seconds of double locking the vehicle the ignition lock is moved to a different position then the system reverts back from double locking to central locking.
If the engine is started after the 45 seconds have elapsed then the double locking remains in force provided the speed of the vehicle does not reach 7 km/h. Once this speed is reached, the system reverts from double locking back to central locking.
Locking/unlocking - driver's door unlocking system
NOTE:The following description only applies if the driver's door unlocking system has been programmed.
If the unlocking button on the radio remote control is only pressed once within 3 seconds, then only the driver's door is unlocked.
If the vehicle was double locked beforehand, then all the other doors switch over to central locking.
If the unlocking button on the radio remote control is pressed twice within 3 seconds then the vehicle is centrally unlocked.
The driver's door unlocking system can be programmed and cancelled with the aid of the radio remote control.
However, this is only possible if the ignition lock is not in position "II".
Reprogramming is performed by simultaneously pressing the unlocking and locking buttons on the radio remote control for at least 4 seconds. The turn signal lamps flash twice to confirm the reprogramming.
On vehicles built from 08/2005, reprogramming can also be performed via the message center integrated in the instrument cluster.
Locking/unlocking - central unlocking
Locking/unlocking - automatic central locking
The vehicle is centrally locked again automatically after unlocking with the radio remote control if within 45 seconds neither a door or the liftgate are opened or the radio remote control is operated.
Programming of radio remote control operations
NOTE:Up to a maximum of four radio remote control operations can be programmed per vehicle.
During the programming process the memory for the known radio remote control operations in the GEM is deleted and the existing and new operations are reprogrammed.
To enter the programming mode for the radio remote controls, turn the ignition lock four times from position "0" to position "II" within 6 seconds.
The programming mode is confirmed with an acoustic signal. Afterwards, the corresponding remote control operations can be programmed within 10 seconds.
To start the programming process, press one of the buttons on the remote control.
The GEM or the instrument cluster (vehicles built from 08/2005) confirms the programming by means of an acoustic signal.
Anti-theft alarm system
The anti-theft alarm system provides a visual and acoustic signal that an unauthorised person is attempting to gain access to the vehicle or that an attempt is being made to turn the ignition key while the anti-theft alarm system is activated.
The system monitors:
- Hood
- Doors
- Liftgate
- Ignition lock
In the event of an alarm, the system actuates a separate signal horn (acoustic alarm) for 30 seconds and the hazard flasher (visual alarm) for 5 minutes.
The anti-theft alarm system is activated with a delay of 20 seconds by centrally locking or double locking the vehicle. To do this the ignition lock must be in the position "0".
After the time delay of 20 seconds the hood, all doors and the liftgate are alarmed, provided they are fully closed.
If the hood, one of the doors or the liftgate are not fully closed then they can be opened without triggering an alarm. If they are then closed, the same time delay of 20 seconds applies before they are alarmed.
The anti-theft alarm system can be switched off by centrally unlocking the vehicle either at the lock on one of the doors or with the remote control.
If the liftgate is opened manually with a key or with the remote control then only the anti-theft alarm for the liftgate is deactivated.
If the liftgate is then closed again, the anti-theft alarm is reactivated for the tailgate after 20 seconds.
The current status of the anti-theft alarm system is stored if the voltage supply to the GEM is interrupted. This means that as soon as the voltage supply to the GEM is restored it reverts to the stored status (if for example the vehicle was alarmed beforehand, it is then re-alarmed).
On vehicles with Thatcham Cat1 alarm system (only available in certain markets) the anti-theft alarm system can be deactivated by pressing the release key on the radio remote control. The anti-theft alarm system is not switched off if the vehicle has been unlocked with the key. In order to deactivate the anti-theft alarm system without the radio remote control, the driver door must first be unlocked with the key. A warning signal sounds for 12 seconds before the alarm is triggered. The anti-theft alarm system is deactivated by turning the key to position "II" in the ignition lock within this time.
NOTE:The interior sensors only operate error-free when all windows and the roof opening panel are completely closed. Furthermore, the sensors must not be covered. The system should not be activated when persons, animals or potentially moving objects are present in the vehicle interior.
NOTE:Do not activate the interior sensors while operating an auxiliary heater. This may trigger the alarm.
On vehicles with enhanced anti-theft warning system (optional), the interior sensors register every movement within the vehicle. They are located in the interior lamp assembly. The interior sensors are activated when double locking is activated.
Liftgate release
The remote release button will not unlock the liftgate if the vehicle is centrally locked or if the vehicle is travelling in excess of 6 km/h.
The remote control can be used to unlock the liftgate by pressing the corresponding button twice within 3 seconds.
Folding exterior mirrors - vehicles built from 08/2005
The folding exterior mirrors can only be activated if this function has been configured in the GEM using WDS or the message center in the instrument.
Battery protection function
The battery protection function prevents the battery from discharging as a result of the interior lighting or the warning sound generator when the engine is switched off.
As soon as the ignition lock is turned to position "I" or "0", a time counter is started in the GEM.
If a door is open the interior lights are switched off after 10 minutes.
If the doors are closed the interior lights, reading lights, luggage compartment lights and the warning sound generator are switched off after 30 minutes.
The battery protection function and the time counter are stopped after the following actions and then if necessary restarted:
- Ignition lock in position "II"
- Opening of a door or the liftgate
- Unlocking of a door or the liftgate (with a key or the remote control)
The battery protection function continues to operate when the GEM is in service mode or diagnostic mode.
Low-power / high-power mode - vehicles built from 08/2005
The GEM has two normal operating modes. In high-power mode, all the functions are executed to their full extent in accordance with the GEM specification. In low-power mode, the GEM functions are minimized in order to spare the battery as much as possible.
When all the following conditions are fulfilled, the GEM switches to low-power mode:
- Ignition lock is in "0" or "I" position.
- Interior lighting is switched off
- Hazard flasher is switched off
- Alarm system is activated or deactivated
- The exterior lighting is not activated via the peripheral lights or headlamp switch-off delay functions
- Automatic closing function is not activated
- Remote control programming mode is not activated
- Service mode is not activated
- CAN is in standby mode
- Remote control receiver signal is stable
- All software function counters are in standby mode
When one of the following conditions occurs in low-power mode, the GEM switches to high-power mode:
- Ignition lock is in position "II" or "III".
- Door switch (incl. liftgate switch or hood switch) status changes
- Audio unit monitoring status changes
- Anti-theft alarm inhibit switch status changes
- Door lock control switch status changes
- Hazard flasher switch status changes
- Central locking button status changes
- Liftgate release switch status changes
- Heated rear window switch status changes
- Remote control signal is received
- CAN is in active mode
When the GEM is in low-power mode, the further power consumption is reduced by changing the remote control receiver reception strategy following certain time periods as follows:
During days 5 to 22 following commencement of low-power mode, it is still possible to lock or unlock the vehicle using the remote control, however the locking button and the unlocking button must be pressed simultaneously for 1.2 seconds in order to ensure that the GEM receives the remote control transmission signals and responds correctly. From day 23 onwards, the vehicle can only be locked or unlocked using the vehicle key.
The GEM can be diagnosed using WDS.
There is also an additional service mode.
This service mode allows testing of various input and output signals.
A signal sounds and the turn signal lamps come on to indicate that service mode has been successfully activated.
The wiper switch must be in the "Off" position for testing the input signals.
The relevant input signals are indicated with an acoustic signal and by the flashing of the turn signal lamps.
The wiper switch must be in the "Intermittent" position for testing of the output signals.
The GEM automatically exits the service mode 20 seconds after the last input.
3 acoustic signals sound and the turn signal lamps come on to confirm that the service mode has been exited.
