The combined rain sensor/light sensor is attached to the windshield, near to the interior rear view mirror.
The ambient light sensor determines the general light intensity. For this purpose, it records 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 lamps in the instrument cluster is transmitted to the GEM.
If the vehicle is suddenly thrown into the shade 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.
In vehicles built from 07/2004 a stepped switch-off of the low beams, side lamps, license plate lamps as well as the instrument cluster and instrument panel illumination is implemented in the GEM. If the ambient light changes from dark to bright, the GEM first switches off the low beams. The side lamps, license plate lamps as well as the instrument cluster and instrument panel illumination are switched off approx. 6 seconds after the low beams have been switched off.
Interior lighting
Depending upon vehicle specification, the interior lighting controlled by the GEM consists of:
- Left and right-hand footwell lamps
- Front and rear dome lamps (in "door contact" switch position)
Depending upon vehicle specification, the interior lamps which can be switched by the operator include:
- Front and rear dome lamps (in "On" switch position)
- Map reading lamps
- Mirror lights in sun visors
- Glove compartment lamp
- Luggage compartment lamp
The interior lighting controlled by the GEM is switched on if one of the following conditions is satisfied:
- One of the vehicle's doors is opened.
- The ignition key is in the "0" or "I" position and the vehicle is unlocked.
- The ignition key is turned from the "II" to the "I" or "0" position.
The interior lighting controlled by the GEM is switched off if all doors are closed and one of the following conditions is satisfied:
- 25 seconds have elapsed since the last door was closed.
- The ignition key is turned from the "0" or "I" to the "II" position.
- The ignition key is in the "0" or "I" position while the vehicle is locked.
The dimmer function is not used if the interior lighting is switched off via the battery protection function.
Battery saver function
In order to prevent the battery from discharging due to permanently switched on current consumers, the left and right-hand footwell lamps and the front and rear dome lamps (in "door contact" switch position) are switched off by the GEM after 10 minutes.
After 30 minutes, the interior lamps which can be switched by the operator (map reading lamps, mirror lights in the sun visors, glove compartment lamp, luggage compartment lamp) as well as the auto-dimming interior mirror (if equipped) are switched off by the power-saving relay.
In addition, all warning signals from the GEM are deactivated after 30 minutes.
The timer is activated if the ignition switch is turned to the "0" or "I" position.
If the interior lamps are switched off due to the battery protection function, they will be switched on again if any of the following conditions is satisfied:
- the ignition switch is turned to the "II" or "III" position
- a door (including the boot or liftgate) is ajar or opened.
- a lock is released.
In this case, the timer is reset again.
Furthermore, the battery protection function is activated by the GEM when the threshold value for low battery voltage is reached.
Heated windshield
If the battery voltage returns to the normal range, disabling of the heated windshield is cancelled. It is then switched on, if it was previously switched on by the driver and if 4 minutes have not yet elapsed since actuation of the heated windshield switch.
If the battery voltage returns to the normal range, disabling of the heated windshield is cancelled. It is then switched off.
Heated rear window and heated external mirrors
NOTE:If a new GEM built after 12/2005 is installed in a vehicle built before 08/2005 during repair work, the LED in the heated rear window switch lights up. Due to this modification to the GEM, a modified heated rear window switch is installed in vehicles built from 08/2005.
The heated rear window and the heated exterior mirrors are switched on by the GEM under the following conditions.
- The switch for the heated rear window is pressed and the ignition switch is in the "II" position.
- The "defrost" function of the air conditioning is activated and the ignition switch is in the position "II".
- The battery voltage has exceeded 16 V for more than 20 seconds (power management strategy). Manual requests to switch off the heated rear window by pressing the button are ignored at this time.
- The engine was started at an outside air temperature below 4°C and an engine temperature below 65°. Manual requests for switching off the heated rear window by pressing the switch are accepted (vehicles built from 03/2007).
If the battery voltage returns to the normal range, disabling of the heated rear window is cancelled. It is then switched on, if it was previously switched on by the driver and if 14 minutes have not yet elapsed since actuation of the heated windshield switch.
On vehicles with door modules, the GEM transmits the request signal for switching on the heated exterior mirrors to the door modules via the CAN bus.
The heated rear window and the heated exterior mirrors are switched off by the GEM under the following conditions
- If more than 14 minutes have elapsed since actuation of the heated rear window switch.
- The ignition switch is turned to the "0" or "I" position.
- The switch for the heated rear window is pressed or the "defrost" function of the air conditioning is deactivated while the heated rear window is switched on.
- The battery voltage has dropped below 10.3 V for more than 20 seconds (power management strategy). Manual requests for switching on the heated rear window by pressing the switch, are ignored at this time.
- More than 14 minutes have elapsed since starting the engine (vehicles built from 03/2007).
If the battery voltage returns to the normal range then the disabling of the heated rear window is cancelled - the heated rear window is then switched off.
On vehicles with door modules, the GEM transmits the request signal for switching off the heated exterior mirrors to the door modules via the CAN bus.
Windshield wash/wipe system
Wiper functions
The windshield wash/wipe system will only operate if the ignition switch is in the "II" or "III" position.
Four wipe functions are available: "one-touch function", "speed 1", "speed 2" and "intermittent mode" or "automatic windshield wipers" (depending upon vehicle specification)".
In "Speed 1" or "Speed 2" mode, the wipers are operating continuously at either normal speed or fast speed.
When the intermittent wipe mode is switched on the windshield wipers operate at normal speed with the following wiper delays:
- Wiper delay 1: 1 second
- Wiper delay 2: 3.5 seconds
- Wiper delay 3: 6 seconds
- Wiper delay 4: 9.5 seconds
- Wiper delay 5: 15.5 seconds
- Wiper delay 6: 22 seconds
NOTE:In the event of a failure, or if the control resistor is not connected the default time for the wiper delay is 8 seconds.
When the windshield washer switch is operated, washer fluid is sprayed onto the windshield. After a short delay designed to protect the wiper blades the wipers perform 2 or 3 wipes at low speed.
If, when the windshield washer switch is activated, the windshield wipers are switched off, then a single wipe is performed 4 seconds after the wipers have returned to the rest position after performing 2 or 3 wipes.
If when the windshield washer switch is activated the wipers are in intermittent mode, and if the selected wiper delay time is longer than 6 seconds, then a single wipe is performed 6 seconds after the wipers have returned to the rest position after performing the 2 or 3 wipes. If an interval of less than 6 seconds selected, afterwipe is not performed.
The afterwipe 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 they are set to intermittent mode.
Automatic wiper function
In vehicles built from 12/2005 without rain sensor, a speed-dependent wiper function is implemented in the GEM on the mid and high-end equipment versions.
When the windshield wipers are switched on, the GEM reduces the wiper speed by one setting if the vehicle is driven at walking speed or comes to a standstill.
When the vehicle speed is increased, the wiper speed automatically returns to the previous setting.
If the wiper lever is actuated during automatic function, the automatic wiper function is switched off and the wiper speed corresponds to the newly-selected setting.
Rain sensor
CAUTION:The automatic windshield wipers must be switched off before the vehicle is driven into a car wash.
CAUTION:If the windshield is iced up, the wipers may only be activated by the rain sensor after the windshield has been completely defrosted.
NOTE:The rain sensor is an optical measuring instrument. Contamination such as oil, grease or dust impair its correct function. Before switching on the automatic windshield wipers, the windshield must be clean in the area of the rain sensor.
The rain sensor is built into a housing which is mounted behind the rear view mirror on the windshield.
The photodiode emits an infrared light beam of known intensity; the emitted light exits through the lens and is reflected by the windshield.
The reflected light beam returns through the lens and reaches the photodiode. The corresponding value taken without moisture on the windshield is used as the reference value for the automatic calibration procedure.
Subsequent deviations from this value cause the windshield wipers to be switched on.
If rain falls on the windshield, then the light reflected by the windshield has a lower intensity. This loss of intensity is registered by the photodiode and, proportionally to the loss of intensity, the module switches on the windshield wipers with the required wipe speed (in intermittent or continuous mode).
When the automatic windshield wipers are switched on (wiper switch set to intermittent mode) the rain sensor is switched on and performs an automatic calibration according to the current conditions at the windshield.
To perform the automatic calibration, the windshield wipers perform a single wipe regardless of whether the windshield is wet or dry.
If the windshield remains dry after this wipe then the windshield wipers stop until moisture is registered on the windshield above the sensor.
On vehicles built from 12/2005, automatic calibration only takes place if the wiper switch was not set to the rain sensing function before the ignition was switched on.
The sensitivity of the rain sensor can be changed by adjusting the control resistor for the intermittent mode of the windshield wipers.
- Adjusting ring position - narrow symbol: high sensitivity
-
The wipers wipe even if only a small amount of water has been measured on the windshield.
- Adjusting ring position - broad symbol: low sensitivity:
-
The wipers only wipe if a large amount of water has been measured on the windshield.
Rear window wash/wipe system
The rear window wash/wipe system will only operate if the ignition switch is in the "II" position.
The GEM changes the wipe interval of the rear window wiper depending upon the windshield wiper switch position.
If the windshield wiper switch is in the "Off", "intermittent mode" or "automatic windshield wiper" (no wiping or low speed) position, then the wipe interval of the rear window wiper is 10 seconds.
If the windshield wiper switch is in the "normal speed", "high speed" or "automatic windshield wiper" (wiping at high speed) position, then the wipe interval of the rear window wiper is 6 seconds.
If the switch for the rear window washer is pressed, then washer fluid is sprayed onto the rear window, and the wiper operates continuously at low speed. When the switch is released the rear window wiper performs another 2-3 wipes.
If the switch for the rear window washer fails while switched ON, or if it is continuously operated for more than 60 seconds, then the switch signal is ignored by the GEM, the wiper returns to the park position and a trouble code is stored for the switch. In the event of the switch sticking in the switched on position, the washer system pump continues to run constantly.
If reverse gear is engaged and the windshield wiper switch is in the normal, high speed or automatic windshield wiper (wiping at high speed) position, the rear window wiper operates continuously until the gearshift lever is moved back to the neutral position.
If reverse gear is engaged and the windshield wiper switch is in the "intermittent mode" or "automatic windshield wiper" (no wiping or low speed) position, then the rear window wiper follows the movement of the windshield wipers. If the wipers windshield wipers leave the rest position, then the rear window wiper also performs a wiping movement.
Headlamp washer system
CAUTION:Do not operate the headlamp washer system for more than 10 seconds, and never with an empty fluid reservoir.
The headlamp washer system operates when the windshield washers are actuated if, at the same time, the light switch is set to "low beam" or if the "autolamp" function has switched on the headlamps. Electrical control is performed by the headlamp washer system relay which itself is controlled by the generic electronic module (GEM).
In order to prevent excessive washer water consumption in vehicles built from 12/2005, the headlamp washer system is only activated on every fourth actuation of the windshield washer switch, provide that 10 minutes have not elapsed since the first actuation of the headlamp washer system. If the windshield washer switch is actuated again after 10 minutes, the headlamp washer system is activated and the timer is restarted.
Speed control
The speed control system consists of a switch unit which is part of the steering wheel component group. The switch unit has a direct interface to the GEM, which in turn communicates with the Powertrain Control Module (PCM).
The signals from the switches of the speed control system are received by the GEM as analogue input voltage signals. The output voltage of the switches of the speed control system is determined by the relevant resistances of the individual switches installed in the switch unit.
The GEM transmits the relevant information as a message to the instrument cluster on the mid-speed CAN bus. From there, the message is forwarded to the PCM on the high-speed CAN bus.
The PCM adjusts the power output of the engine in order to maintain the selected vehicle speed.
Central locking
Locking/unlocking - central locking
The central locking system locks all doors, the liftgate and the tank flap, so that none of these can be opened from the outside of the vehicle. The locking of the tank flap is linked to the locking/unlocking of the driver's door.
On vehicles with door modules, all door lock motors and door lock switches are controlled via the door lock modules. The door ajar switch signals are transmitted directly to the GEM.
On vehicles without door modules, all locking/unlocking functions are controlled via the GEM.
Vehicles with door modules can be identified by means of the two-stage window control switch.
If one of the front doors is not fully closed during the central locking procedure, all doors are locked and then unlocked again. This procedure is signaled acoustically.
If one of the rear doors, the liftgate or the hood (on vehicles with ant-theft alarm system) are not completely closed, all the doors are nevertheless locked centrally.
Once the open door, the open liftgate and/or hood (on vehicles with anti-theft alarm system) is closed, the central locking is confirmed by the turn signals flashing briefly twice.
Locking/unlocking - double locking
The double locking system locks all doors so that they cannot be opened from outside the vehicle. In addition to the central locking function, the double locking function also disconnects the inside door handles from the locking mechanism, as a result of which it is also no longer possible to open the doors from inside the vehicle.
The double locking will only operate if the ignition lock is in the position "0" or "I".
If the ignition lock has been turned to the position "II" or one of the rear doors is not fully closed then the vehicle is centrally locked but not double locked.
If, on a double-locked vehicle, the ignition switch is turned to the "II" or "III" position and a valid PATS signal is transmitted, the system switches from double locking to central locking.
Double locking is confirmed by two short flashes of the turn signal lamps. No flashing takes place for central locking on a vehicle with double locking.
Locking/unlocking - central unlocking
The central unlocking system unlocks all of the doors on the vehicle including the tank flap.
If the vehicle has been configured for unlocking via the driver's door lock and the "unlocking" button on the remote control is only pressed once, then just the driver's door and the tank flap are unlocked.
If the "unlocking" button on the remote control is then pressed again within 3 seconds the remaining doors are unlocked via the central unlocking function.
If the vehicle was double locked beforehand, then the other doors are centrally locked, whereas the driver's door is unlocked.
Unlocking of the vehicle with the ignition switched off, is confirmed by one long flash of the turn signal lamps.
Locking/unlocking - automatic re-locking
The automatic re-locking function returns the locking system of the vehicle to its last status if it was centrally locked or double locked and the following conditions are satisfied:
- The vehicle is unlocked via remote control.
- Neither a door nor the liftgate has been opened within 45 seconds.
- The ignition is not switched on.
Liftgate
The liftgate unlocking mechanism unlocks the liftgate if the ignition switch is either in position "0" or position "1" and one of the following conditions is met:
- The exterior liftgate release button on the vehicle is pressed with the driver door unlocked.
- The liftgate release button on the radio remote control is pressed twice within 3 seconds.
The liftgate unlocking function unlocks the liftgate if the ignition switch is in either position "II" or "III" and the vehicle speed is below 7 km/h and one of the following conditions is satisfied:
- The exterior liftgate release button on the vehicle is pressed (vehicles built up to 03/2007).
- A vehicle door has been opened and the exterior liftgate release button on the vehicle is pressed (vehicles built from 03/2007). In this case, the vehicle must have exceeded the vehicle speed of 7 km/h at least once.
- The liftgate release button on the radio remote control is pressed twice within 3 seconds.
When installing a new GEM, the internal receiver in the GEM must be enabled using the IDS on vehicles with radio remote control. It should be noted that different GEMs must be used, depending on the permissible radio frequency (315 MHz or 434 MHz) in the relevant country.
Key-free vehicle system
A key-free vehicle system is optionally available, in which receivers on both front door handles, in the rear section and in the interior check whether a valid "passive key", which is programmed to the vehicle, is within the detection area in order to prepare the locking mechanism for opening the doors and then to enable the ignition lock, following actuation of the clutch pedal (vehicles with manual transmission) or brake pedal (vehicles with automatic transmission).
The reception signals are transmitted to the key-free vehicle system module, which then controls all further locking/unlocking functions.
After leaving the vehicle, it can be locked via sensors on the front door handles or on the liftgate handle (press once) or double locked (press twice). In this case, a request signal (lock/unlock) is transmitted by the key-free vehicle system module to the GEM via the mid-speed CAN bus. The GEM then actuates the door modules via the mid-speed CAN bus, which unlock or lock the vehicle.
All door opening/closing functions can also be performed via the remote control buttons on the "passive key". In addition, there is an emergency key in the "passive key" which, together with an adapter, serves to open and start the vehicle in an emergency.
On keyless vehicles, there is no internal receiver for the locking system in the GEM. Consequently, only the receiver in the interior is used.
Smart Charge system
In addition to the familiar functions, the Smart Charge system also performs the following functions:
- Automatic deactivation of non-critical high power electrical consumers when the battery voltage is low in order to reduce the level of current drawn.
- Automatic activation of non-critical high power electrical consumers when the battery voltage is excessively high in order to protect components which are sensitive to increased voltages.
The battery charging current is optimized through continuous calculation of the battery temperature and monitoring of the alternator output voltage.
The alternator load is signaled to the PCM in order to provide it with an early indication when an electric component is to be switched on or off, thereby also providing information about imminent changes to the amount of torque demanded by the alternator. By evaluating this information the PCM is capable of increasing the stability of the engine under idling.
The two remaining functions of the Smart Charge system are controlled by the GEM.
Electrical consumers are switched off when the battery voltage is low if the GEM determines (as a result of the message received from the PCM on the CAN bus via the instrument cluster) that the battery voltage has dropped below the threshold value.
If the threshold value for low battery voltage is reached, the GEM automatically deactivates the following consumers, in this sequence and with a 5-second time interval:
- Heated windshield
- Heated rear window
- Electric booster heater (vehicles with diesel engines)
- Air conditioning
If the battery voltage then increases above the lower threshold value, the disabling of all previously-deactivated electrical consumers is cancelled by the GEM. They then have switched off status and must be switched back on by the driver.
Electrical consumers are switched on when the battery voltage is excessively high if the GEM determines that the battery voltage has increased above the threshold for overvoltage and the charging system warning indicator has come on.
If the threshold value is reached, the GEM automatically activates the following consumers, in this sequence and with a 5-second time interval:
- Heated rear window
- Heated windshield
If the battery voltage again falls below the threshold value, the heated rear window and the heated windshield are automatically deactivated by the GEM. However, if they were switched on by the driver before the automatic activation, they will then be switched on again in turn with a 5-second time interval.
Ambient air temperature
The outside air temperature sensor is connected to the GEM via two wires. It measures the outside air temperature to an accuracy of around ±0.5 °C. The GEM transmits the outside air temperature via the mid-speed CAN bus, where it can be evaluated by various systems.
Ignition overload protection
The ignition overload protection intermittently disconnects certain circuits in order to restrict the current being drawn from the battery while the starter motor is operating.
The position of the ignition switch is transmit by the instrument cluster via the mid-speed CAN bus.
The ignition overload protection relay which is integrated in the battery junction box is activated by the GEM if the message "ignition switch in position III" is received from the instrument cluster.
Power windows
Vehicles with and without door modules
To operate the power windows, the ignition key must be in the "II" or "III" position. The power windows open or close the door windows when the switch is moved to the corresponding position.
The movement of the glass stops if the window regulator button is released or if the ignition key is turned from the "II" or "III" position to "I" or "0".
The driver door window can only be operated via the driver door switch; the other windows can be opened and closed via the driver door switch panel or the relevant door switch.
Vehicles with door modules
If the front passenger door window or one of the rear door windows is operated via the switch on the driver door switch panel, then the driver's door module receives the wire-transmitted signal from the switch and forwards it to the relevant door module via the CAN bus, which then moves the window glass in the appropriate direction.
A switch is provided on the driver door switch panel to disable the window regulator switches of the rear doors.
Brake fluid level
For normal brake fluid levels, the brake fluid level switch is closed and switches a ground signal to the GEM via a wire.
If the brake fluid level falls below the threshold value and the level switch opens for more than two seconds, the GEM generates a CAN signal and transmits it to the instrument cluster.
Change in fuse designation
With the introduction of the new GEM generation 7M5T-14A073-XX, the fuse designations have been changed.