auto diagnostic advisor: Rain sensor

The rain sensor is an optical measuring instrument. Contamination such as oil, grease, dust or faulty wiper blades will prevent the system from working properly. 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 rain sensor (1) consists of an opto-electronic measuring and evaluation circuit. The sensor can calculate 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 set to the required wipe speed by the generic electronic module (GEM).

Mode of operation of the rain sensor

The rain sensor consists of three optical components:

an LED
a photodiode
a lens

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 enters back through the lens and then reaches the photodiode. The corresponding value taken without moisture on the windshield is used as the reference value for the automatic calibration process.

Subsequent deviations from this value cause the windshield wipers to be switched on.

If rain lands 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 wipe function is switched on (wiper lever to intermittent position) the wipers are only activated automatically if the rain sensor registers water on the windshield.

It is not necessary to calibrate the rain sensor, as this has already been done at the factory.

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 - wide symbol: High sensitivity

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The wipers wipe even if only a small amount of water has been measured on the windshield.
Adjusting ring position - narrow symbol: Low sensitivity

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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 position "II".

If the windshield wiper switch is in the "Off", "Intermittent mode" or "Automatic wipe" (no wiping or low speed) position, then the wipe interval of the rear window wiper is 10 seconds.

If, on a vehicle equipped with a rain sensor, the windshield wiper switch is set to intermittent mode, speed 1 or speed 2 and rain is detected on the windshield then the rear wiper will come on in intermittent mode with a delay of 10 seconds between wipes.

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 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 will operate continuously until the gearshift lever is moved back to the neutral position.

If reverse gear is engaged and a single wipe of the windshield wiper is performed via the one-touch function then the rear wiper also performs a single wipe.

Headlamp washer system

The headlamp washer system will start to operate when the windshield washer function is activated if, at the same time, the light switch is set to "dipped beam" or the headlamps have been switched on by the "automatic headlamps" function. 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 water consumption, the headlamp washer system is only activated every fourth time the windshield wash/wipe switch is operated, provided the time elapsed since the first operation of the headlamp washer system does not exceed 10 minutes. If the windshield wash/wipe switch is activated again after 10 minutes the headlamp washer system is activated and the time encoder is restarted.

If the wash water level warning lamp on the instrument cluster comes on because the wash water level in the washer reservoir is too low then the headlamp washer pump is no longer activated until the washer reservoir is topped up.

central door locking

Locking/unlocking – central locking

The central locking system locks all doors and the liftgate, so that none of these can be opened from the outside of the vehicle.

On vehicles with door modules in the front and rear doors, all door lock motors and door lock switches are controlled via the door locking modules. The signals from the door contact switches are forwarded directly to the GEM.

On vehicles without rear door modules the door lock motors are also directly actuated by the GEM.

Vehicles without rear door modules only have manually operated windows in the rear.

Vehicles with 4 door modules can be identified by the two-stage window regulator switches in the front and rear.

The central locking is actuated if one of the following conditions is satisfied:

A key is inserted into one of the door locks and turned to the "locking" position.
The locking button on the remote control is pressed once.
The inside door handle is pressed (if equipped).

If one of the doors is not properly closed when the central locking function is performed then all doors are locked and unlocked again. This procedure is signaled acoustically.

The turn signal lamps flash twice when the vehicle has been successfully centrally locked.

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 system also disconnects the door opening levers from the locking mechanism. This means that the doors can no longer be opened from inside the vehicle.

The double locking mechanism only works when the ignition key is not in the ignition lock.

The double locking is activated if one of the following conditions is satisfied:

A key is inserted into a door lock and turned to the "locking" position twice within 3 seconds.
The locking button on the remote control is pressed twice within the space of 3 seconds (if the vehicle is configured for activation of the double locking upon a double press of the locking button on the remote control).

If the ignition key has been turned to position "I" then the vehicle is centrally locked but not double-locked.

If on a double-locked vehicle the corresponding ignition key is inserted into the ignition, the system switches over from double locking to central locking.

The turn signal lamps flash to confirm when the vehicle has been double locked.

The turn signal lamps do not flash when the vehicle is centrally locked.

Locking/unlocking – central unlocking

The central unlocking system unlocks all of the doors on the vehicle including the liftgate.

The central locking is actuated if one of the following conditions is satisfied:

The door lock is turned to the unlocking position.
The release button on the radio remote control is pressed once (provided that the vehicle is not configured for unlocking via the driver's door lock).
The release button on the radio remote control is pressed twice within 3 seconds (provided that the vehicle is not configured for unlocking via the driver's door lock).
The door opening lever on a front door is pulled to the unlocking position on a centrally locked vehicle.
The door opening lever on a vehicle equipped with a keyless vehicle module is pulled to the unlocking position; to do this, a transmitter which has been configured for the vehicle must be located within the reception range of the vehicle.

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 is 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 function

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 liftgate unlocking button on the outside of the vehicle is pressed, provided the vehicle has been unlocked either via the driver's door lock or centrally.
The liftgate unlocking button on the remote control is pressed once (provided the vehicle has been configured for liftgate unlocking after a single press of the button on the remote control).
The liftgate unlocking button on the remote control is pressed twice within 3 seconds (if the vehicle has not been configured for liftgate unlocking after a single press of the button on the remote control).

If the liftgate is unlocked via the remote control while the vehicle is locked then it is automatically locked again when the vehicle is re-locked.

Keyless vehicle system

A keyless vehicle module for locking and starting is available as an option. With this system, receivers on the two front door handles and at the rear of the vehicle check whether a valid "Passive Key" which has been programmed for the vehicle is present in the detection area in order to prepare the locking mechanism for opening of the doors.

Subsequently, sensors in the interior detect whether a valid "Passive Key" which has been programmed for the vehicle is present in the detection area in order to enable the ignition lock after operation of the clutch pedal (vehicles with a manual transmission) or brake pedal (vehicles with an automatic transmission).

The reception signals are transmitted to the keyless vehicle module, which then controls all further locking/unlocking functions.

Depending on how the system is programmed, operation of the driver's door handle will unlock either all of the doors or just the driver's door. If the vehicle is programmed for "single door unlocking" and other door handles are operated in addition to the driver's door handle then the vehicle is centrally unlocked.

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 keyless vehicle 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.

Passive Start

A keyless vehicle module for starting is available as an option. With this system, sensors in the interior detect whether a valid "Passive Key" which has been programmed for the vehicle is present in the detection area in order to enable the ignition lock after operation of the clutch pedal (vehicles with a manual transmission) or brake pedal (vehicles with an automatic transmission).

Once the ignition lock has been enabled, the vehicle can be started via the starter button in the dash panel console provided the transmission is in neutral and the clutch is fully depressed (vehicles with a manual transmission) or provided the transmission is set to "Park" and the brake pedal is fully depressed (vehicles with an automatic transmission).

The starter button is pressed again to switch the engine off, whereby the vehicle speed must be below the maximum limit of 7 km/h.

The engine can be stopped at any vehicle speed by pressing and holding the starter button or by pressing it repeatedly.

It is possible to restart the engine within 10 seconds of switching the engine off without repeat detection of a valid "Passive Key". The only requirement in this instance is that the correct pedal for the type of transmission is depressed.

If a valid "Passive Key" which has been programmed for the vehicle is in the detection area of the ignition lock and the starter button is pressed without the clutch pedal (vehicles with manual transmission) or brake pedal (vehicles with automatic transmission) being depressed, the ignition only is switched on but the engine cannot be started. Pressing the starter button again switches the ignition back off.

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.

By receiving the forwarded alternator load signal, the PCM is given early warning whenever an electric consumer is switched on or off. This means that the PCM receives information about imminent changes in the torque drawn by the alternator. By evaluating this information the PCM can provide a higher level of idling stability.

The two remaining functions of the Smart Charge System are controlled by the GEM.

Electrical consumers are switched off due to low voltage when the GEM determines (on the basis of the message received from the PCM on the CAN bus via the instrument cluster) that the battery voltage has dropped below the threshold.

When the threshold for low battery voltage is reached the GEM automatically deactivates the following consumers - in this order and with a gap of 5 seconds between each: