LDW Lane Departure Warning

The lane departure warning (LDW) is a driver assistance system that - as of 03/07 on the E60/E61 - supports driving by informing the driver at an early stage by means of a steering wheel vibration of inadvertent deviations from the course of his or her vehicle and animates the driver to countersteer. If a lane marking line is crossed, the driver is warned by the system if he or she has not indicated or acted otherwise (braking / accelerating). The lane markings on the right and left of the driving lane are detected with a camera.

Brief description of components

The following components are described for the lane departure warning:

• Lane departure warning camera
  
• Vibration motor
  
• LDW control unit
  
• MFL button for lane departure warning
  

System circuit diagram

Lane departure warning camera

The camera is installed in the area of the interior mirror behind the windscreen; it transmits the camera images across a data line to the control unit.

Vibration motor

The vibration motor and the associated electronics are fully integrated in the steering wheel. To generate the vibration, there is a small counterbalance weight on the axle of the vibration motor.

LDW control unit

The control unit contains the software that uses the camera images to determine the position of the vehicle in the driving lane. The control unit of the lane departure warning searches in the images recorded by the camera by means of image processing to find possible lane markings.

MFL button for lane departure warning

The lane departure warning is switched on and off using the button shown above on the multifunction steering wheel. Each push of the button switches the lane departure warning on or off.

System functions

The following system functions are described for the lane departure warning:

• Driving lane detection
  
• Warning output
  
• Display of the lane departure warning
  

Driving lane detection

The system is available as of a speed of 70 kph. If driving lanes are detected, the lane departure warning is also ready to warn. At speeds below 70 kph, an indication of the availability as of 70 kph appears in the instrument cluster for approx. 3 seconds when the system is activated.

Warning output

The lane departure warning only issues a warning to the driver if the system is switched on and available.

The warning is perceived as a vibration on the steering wheel.

Display of the lane departure warning

Note for Service department:

General information

The LDW is only operational when it has been calibrated. To calibrate the system, an internal algorithm must be started.

Calibration

In the event of replacement of the camera or windscreen, calibration of the system is required, as in these cases the position of the camera - and thus of the system sensor - could have changed. If the control unit is replaced, no calibration is required. In this case, the adjustment data stored in the camera is transferred to the control unit and stored there.

Diagnosis instructions

The service function <Calibration lane departure warning> can be used to calibrate the camera or to query the status of the calibration. The calibration takes place in two steps:

• Unobstructed view detection. The unobstructed perspective can be determined, for example, in that a person walks past in front of the camera. If this test step is completed successfully (proper camera image), the calibration is started automatically.
  

• Calibration run. The calibration takes place by means of a calibration run (as of 30 kph); this can be carried out by the customer. In the event that the camera test fails, the calibration process is aborted and must be restarted after remedying any possible disturbances.
  

If the calibration was unsuccessful, two fault code memory entries are set in the control unit:

• A92B: camera not yet calibrated
  

• A92C:
  
  • present at the moment -> calibration triggered but not successfully completed.
    
  • not present at the moment -> successfully completed.
    

With a successful calibration of the camera, the vehicle identification number is written into the camera. Only when the vehicle identification number of the camera, of the control unit and of the vehicle match can the system be activated.