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Blind Spot Assist, Function - GF54.71-P-0003GR

MODEL 166 up to model year 2016 with CODE 234 (Blind Spot Monitoring) 

MODEL 166 up to model year 2016 with CODE 237 (Active Blind Spot Assist) 

With CODE 234 (Blind spot assist) 

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With CODE 237 (Active blind spot assist) 

G12079358

Function requirements, general 

Blind Spot Assist, general 

The Blind Spot Assist monitors the rear and side areas of the vehicle using short range radar and, if necessary, informs the driver that an intentional lane change (turn signal active) is not recommended at this time. In the wider sense, the Blind Spot Assist serves as an extension of the outside mirror; under no circumstances is the driver relieved of his/her responsibility of safely carrying out the lane change. In the respective outside mirror, a visual indicator indicates the status of the Blind Spot Assist and warns of critical situations during a lane change (i.e. a vehicle is in the "blind spot"). In addition, an acoustic warning can also be given.

The visual warning output takes place via the following components:

The acoustic warning is output via the warning buzzer in the instrument cluster.

IMPORTANT The electronic ignition lock control unit is the central interface (gateway) for the exchange of function-relevant data for control units which are connected to the various Controller Area Network (CAN) bus systems.

A distinction is currently made between the following Blind Spot Assist variants:

Blind Spot Assist:

The area which cannot be observed via the outside mirror and inside rear-view mirror is monitored by the following components:

All relevant data are evaluated by the rear bumper radar sensors, whereby the right rear bumper radar sensor requests the warning output.

IMPORTANT The rear bumper radar sensors operate according to the "master-slave" principle. The master or slave function can be determined via the connector coding. The master function is defined for the right rear bumper radar sensor. In other words, the left rear bumper radar sensor transmits its requests to output warning and readiness messages over chassis CAN 1 to the right rear bumper radar sensor, which then evaluates the information from both rear bumper radar sensors and passes on corresponding requests via chassis CAN 1.

Active Blind Spot Assist:

Active Blind Spot Assist builds upon the functionality of Blind Spot Assist. Active Blind Spot Assist can additionally perform brake system interventions to correct the course, taking the surroundings of the vehicle into account. Active interventions by the brake system are conducted on a wheel-specific basis and exert a course-correcting influence. If a risk of collision is detected with vehicles that are in the blind spot, then an accident can be avoided or the consequences of the accident lessened.

The area which cannot be observed via the outside mirror and inside rear-view mirror is monitored by the following components:

The course-correcting intervention is dependent on the road space in front of the vehicle being monitored to avoid any collisions with other road user (incl. oncoming traffic) because of any change in direction. Monitoring of the road in front of the vehicle is performed by the following components:

The front bumper DISTRONIC (DTR) sensors and rear bumper radar sensors transmit the corresponding data over the sensor CAN to the video and radar sensor system control unit. The DISTRONIC electric controller unit transmits the corresponding data over the vehicle dynamics CAN to the video and radar sensor system control unit. All relevant data are evaluated by the video and radar sensor system control unit.

Illustration of the principle of Blind Spot Assist, shown on model 166.0 

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The following information is read in by the rear bumper radar sensors (with code (234) Blind Spot Assist) or by the video and radar sensor system control unit (with CODE 237 (Active Blind Spot Assist)):

Status of circuit 15:

The electronic ignition lock control unit transmits the status of circuit 15 to the rear bumper radars sensors or video and radar sensor system control unit via chassis CAN 1.

Status of "Blind Spot Assist" status:

The instrument cluster sends the status of the "Blind Spot Assist" function (switched on or off) via chassis CAN 2, the electronic ignition lock control unit and chassis CAN 1 to the rear bumper radar sensors or to the video and radar sensor system control unit.

"Engine running" or "Drive train operational" signal:

The CDI control unit or the ME-SFI [ME] control unit sends the "Engine running" or "Drive train operational" signal via chassis CAN 1 to the rear bumper radar sensors or to the video and radar sensor system control unit.

Vehicle in forward movement, vehicle speed:

Forward movement is defined via the wheel rotation direction. The vehicle speed is calculated on the basis of the wheel speeds. The wheel rotation directions and the wheel speeds are recorded by the rpm sensors. The Electronic Stability Program control unit reads in the signals from the rpm sensors directly and sends these via chassis CAN 1 to the rear bumper radar sensors or to the video and radar sensor system control unit.

Gear range status:

The fully integrated transmission control unit sends the status of the gear range via drive train CAN, CDI control unit or ME-SFI [ME] control unit and chassis CAN 1 to the rear bumper radar sensors or to the video and radar sensor system control unit.

Trailer recognition (with CODE 550 (Trailer hitch)):

If a trailer is detected, the trailer recognition control unit sends the "Trailer detected" status via interior CAN, electronic ignition lock control unit and chassis CAN 1 to the rear bumper radar sensors or to the video and radar sensor system control unit.

Status of service brake, status of yawing moment interface (with CODE 237 (Active Blind Spot Assist)):

The Electronic Stability Program control unit sends the status of the service brake and the yawing moment interface via chassis CAN 1 to the video and radar sensor system control unit.

IMPORTANT The yawing moment interface that is integrated in the Electronic Stability Program control unit sends out a status signal to enable a course-correcting braking torque.

The Blind Spot Assist system includes the following subfunctions:

Measuring procedure function sequence 

Vehicles are detected based on the radar measuring procedure.

Electromagnetic waves are bundled and sent out as so-called primary signals here by the short and long range radar sensors. If these meet a vehicle, they are reflected by it and received again by the corresponding radar sensor as secondary signals. These signals are used to calculate the distance and the speed of the detected object as well as its angle relative to the vehicle.

The short-range radar sensors are ultra-wide band radar sensors with the following properties:

IMPORTANT This is switched off automatically in countries in which the 24 GHz radar sensor system is not approved.

The range up to maximum s = 200 m in front of the vehicle is monitored on vehicles with CODE 237 (Active Blind Spot Assist) by the DISTRONIC electric controller unit (long range radar). The monitoring range distance is flexibly configured and is regulated to match the vehicle speed. The DISTRONIC electric controller unit transmits the corresponding data over the vehicle dynamics CAN to the video and radar sensor system control unit.

Detection ranges of radar sensor system with CODE 234 (Blind Spot Assist), shown on model 166.0 

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IMPORTANT The rear radar sensor system coverage area is based on the angles of the radar waves. These are extrapolated by the respective rear bumper radar sensor to produce the actual monitoring ranges.

Detection ranges of radar sensor system incl. front road space monitoring with CODE 237 (Active Blind Spot Assist), shown on model 166.0 

G12079361

IMPORTANT The rear and front radar sensor system coverage areas are based on the angles of the radar waves. These are extrapolated by the video and radar sensor system control unit to calculate the actual monitoring ranges.

Display of actual rear monitoring ranges (with CODE 234 (Blind Spot Assist) or CODE 237 (Active Blind Spot Assist)), shown on model 166.0 

G12079362

Automatic deactivation of radar sensor system in Western Europe (model 166.0 up to 30.11.2012, model 166.8 up to 30.06.2013):

Due to legal requirements on the 24 GHz radar system (short range radar) in Western Europe, the short range radar sensor system is automatically switched off in certain protected areas around radioastronomy stations. In other words the Blind Spot Assist is not functional in these ranges. The protected areas around radio astronomy stations are stored in the rear bumper radar sensors or in the video and radar sensor system control unit.

The radio (with CODE 523 (MB Audio 20 radio) or CODE 510 (Audio 20 with CD changer)) or the COMAND controller unit (with CODE 512 (COMAND APS with DVD changer) or CODE 527 (COMAND APS with single DVD drive (with navigation))) constantly sends current GPS coordinates (global positioning system) over the interior CAN, electronic ignition lock control unit and the chassis CAN 1 to the rear bumper radar sensors or to the video and radar sensor system control unit.

IMPORTANT The radio (with code (523) MB Audio 20 radio or code (510) Audio 20 with CD changer) does not read in the GPS coordinates directly but receives them over the telematics CAN from the navigation module (with CODE 509 (Navigation box)), which is connected to the vehicle CAN bus system through the holder for the navigation module (with CODE 508 (Navigation box preinstallation) or CODE 509 (Navigation box)).

The short-range radar sensor system is shut off based on these. With Active Blind Spot Assist, the message "Radar sensor system automatically switched off, see operator's manual" is shown on the multifunction display of the instrument cluster. The Blind Spot Assist readiness and warning indicators light up in yellow.

If the vehicle is parked in a restricted area, then when it is started up again the GPS coordinates are used for position finding. The driver is notified again that the radar sensor system was automatically switched off. If the vehicle leaves the restricted area, the radar sensor system is automatically switched on again. The "radar sensor system automatically switched off, see operator's manual" message is canceled and the yellow Blind Spot Assist readiness and warning indicator lamps are switched off.

On model 166.0 as of 01.12.2012, model 166.8 as of 01.07.2013 the radar sensor system is no longer automatically switched off. Use of the reduced frequency band range from f = 24.25 GHz to 25.65 GHz means that this is no longer necessary. Both the NATO band and the radio astronomy band are left out. Operation of the radar sensor system within the restricted areas of the radio astronomy stations is thereby rendered possible. Consequentially, localization of the vehicle through GPS is no longer required.

IMPORTANT Manual switching on/off of the radar sensor system:

The "Vehicle settings" menu in the instrument cluster also enables the radar sensor system to be manually switched off and on again.

Model 166.0 up to 30.11.2012, model 166.8 up to 30.06.2013: If the radar sensor system was automatically switched off within a restricted area, the manual switch-on option is no longer available and the following message is shown "Radar sensor system automatically switched off, see operator's manual".

Function sequence for displaying system and warning messages 

When circuit 15 is switched on, the Blind Spot Assist readiness and warning indicators are switched on for t = 1.5 s turning first red then yellow. When a speed of v > 30 km/h is reached the Blind Spot Assist readiness and warning indicators are switched off and the Blind Spot Assist is ready for warning.

If a function error is determined, a corresponding message is shown on the multifunction display and the Blind Spot Assist readiness and warning indicators light up in yellow. The status of functional readiness is transmitted by the rear bumper radars sensors or the video and radar sensor system control unit via chassis CAN 1, electronic ignition lock control unit and interior CAN to the respective front door control unit, which then actuates the corresponding Blind Spot Assist readiness and warning indicator. The request to output fault messages is sent by the rear bumper radars sensors or the video and radar sensor system control unit via chassis CAN 1, electronic ignition lock control unit and chassis CAN 2 to the instrument cluster.

If, at a speed of v30 to 250 km/h, a vehicle is located in the radar sensor system detection range, the driver receives a warning stating on which side of the vehicle the vehicle is in the blind spot by means of the Blind Spot Assist readiness and warning indicator turning red in the outside mirror. When vehicles are passing, they are recognized and a warning is issued regardless of their relative speed to the vehicle with Blind Spot Assist. Due to the short reaction time when the difference in speed is high, the warning message output sometimes does not have any added value. If the driver still attempts to change the lane and indicates this by operating the combination switch (sets turn signal) despite the illumination of the Blind Spot Assist readiness and warning indicator, a dual warning tone is also output via the warning buzzer in the instrument cluster that is actuated directly by the instrument cluster. The Blind Spot Assist readiness and warning indicator flashes on and off. If the vehicle leaves the radar sensor system's sensing range, the red flashing Blind Spot Assist readiness and warning indicator is switched off.

IMPORTANT The signal curve for issuing warning messages corresponds to that of the display for function readiness.

The steering column tube module control unit reads in the switch position of the combination switch directly and sends it over chassis CAN 1 to the rear bumper radar sensors or video and radar sensor system control unit.

Blind Spot Assist readiness indicator, shown on the left side of the vehicle 

G12079363

Blind Spot Assist warning indicator shown on the left side of the vehicle 

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The following table contains the requirements for displaying system readiness and for showing the visual warning messages.

Operating state  Blind Spot Assist readiness and warning indicator off Blind Spot Assist readiness and warning indicator lights up in yellow. Blind Spot Assist readiness and warning indicator lights up in red. Blind Spot Assist readiness and warning indicator flashes on and off in red.
Circuit 15 OFF X      
Circuit 15 ON (t < 1.5 s)     X  
Circuit 15 ON (t > 1.5 s)   X    
Engine running or drive train operational.   X    
Vehicle accelerates X      
Vehicle speed v > 250 km/h X      
Vehicle decelerates, vehicle speed v ≤ 25 km/h   X    
Trailer recognized (with CODE 550 (Trailer hitch))   X    
Drive position "R" engaged X      
Vehicle recognized in blind spot     X  
Vehicle detected in blind spot and turn signal set       X
Course-correcting brake intervention active (with CODE 237 (Active Blind Spot Assist))       X
Radar sensor system automatically deactivated (model 166.0 up to 30.11.2012, model 166.8 up to 30.06.2013)   X    
Fault in Blind Spot Assist system   X    

Additional function requirements for active intervention by the brake system (with CODE 237 (Active Blind Spot Assist)) 

IMPORTANT The status information for the driving assistance and driving safety systems ABS, ASR, BAS, ESP® and PRE-SAFE brake as well as for the yaw-moment interface is sent by the Electronic Stability Program control unit over the chassis CAN 1 to the video and radar sensor system control unit.

Function sequence for active intervention by the brake system (with CODE 237 (Active Blind Spot Assist)) 

If the video and radar sensor system control unit detects the threat of an imminent side collision with a vehicle during a lane change, it requests course-correcting intervention by the brake system. The video and radar sensor system control unit sends this request over chassis CAN 1 to the Electronic Stability Program control unit which then implements this accordingly by actuating the traction system hydraulic unit. The Electronic Stability Program control unit selectively brakes individual wheels and moves the vehicle back onto a collision-free course.

IMPORTANT If the driver countersteers against the intervention by the brake system (overrides the intervention by the brake system) or accelerates the vehicle, the intervention by the brake system is immediately canceled. The driver assistance or driving-safety systems ABS, ASR, BAS, ESP® and PRE-SAFE brakes are of a higher priority than the Active Blind Spot Assist. Active control intervention functions from these systems result in cancellation of the active intervention by the brake system.

IMPORTANT If the ABS system is actively intervening, a Blind Spot Assist intervention by the brake system is not initiated. During such an intervention by the brake system, the ABS may reduce the intensity of the intervention by the brake system, the intervention by the brake system itself however is continued with.

Course-correcting interventions by the brake system are always suppressed, when one of the following conditions occurs:

IMPORTANT Information on tire pressure monitoring is available in the separate "Tire pressure monitor function" or the "Tire pressure loss warning (RDW) function" description.

Steering movements are recorded by the steering wheel angle sensor. The steering column tube module control unit reads in the steering wheel angle sensor data and sends information on the steering wheel angle over chassis CAN 1 to the video and radar sensor system control unit.

The following graphics show situations in which course-correcting interventions by the brake system are suppressed.

Shows model 166.0 

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If vehicles (2) are located very close in the blind spot on both sides of the vehicle (1), a course-correcting brake intervention is suppressed.

Shows model 166.0 

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If an obstacle (8) is located at the side next to the vehicle (1), the position of which cannot be determined, a course-correcting brake intervention in the direction of the obstacle (8) is suppressed.

Shows model 166.0 

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If an obstacle (8) is detected on one side of the vehicle (1), course-correcting brake intervention in the direction of the obstacle (8) is suppressed.

Shows model 166.0 

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In the event of an imminent risk of collision with a preceding vehicle (10) and a vehicle in the blind spot (2) a course-correcting intervention by the brake system is suppressed.

IMPORTANT An acoustic warning is not issued!

Shows model 166.0 

G12079369

In the event of an imminent risk of collision with a stationary obstacle (8) and a vehicle in the blind spot (2) a course-correcting intervention by the brake system is suppressed.

IMPORTANT An acoustic warning is not issued!

Shows model 166.0 

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In the event of oncoming traffic (9), a course-correcting brake intervention is limited in intensity so that any collision with oncoming traffic (9) is avoided.

  Electrical function schematic, blind spot assistant MODEL 166 up to model year 2016 with CODE 234 (Blind Spot Monitoring) without CODE 237 (Active Blind Spot Assist) PE54.71-P-2051-97NAA
MODEL 166 up to model year 2016 with CODE 237 (Active Blind Spot Assist) without CODE 234 (Blind Spot Monitoring) PE54.71-P-2051-97NAB
  Overview of system components for driver assistance systems   GF54.00-P-9998GR
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