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(DISTRONIC Plus Incl. Bas Plus And Pre-Safe (R) Brake, Function - GF30.30-P-0006RD)

Model 172.4 

up to model year 2016 

with code 233 (DISTRONIC PLUS) 

G13845634Courtesy of MERCEDES-BENZ USA

Shown on model 172.4 

Function requirements, general 

IMPORTANT The SSC function is described elsewhere.

DISTRONIC PLUS incl. BAS PLUS (BAS PLUS) and PRE-SAFE® brake, general points 

The DISTRONIC PLUS regulates the speed and distance relative to the vehicle in front in a vehicle speed range of v = 0 to 200 km/h and v = 200 to 0 km/h automatically according to the driver's request. The PRE-SAFE® brake function permanently determines the potential danger of a collision occurring and initiates appropriate measures to mitigate the effects of a collision in critical situations. Furthermore, there is a distance warning function contained therein which advises the driver about a vehicle driving immediately ahead which is too close. An optical and acoustic warning is issued before any possible collisions with vehicles or stationary obstacles on the vehicle's own lane.

If the driver reacts to the collision critical warning with an emergency braking maneuver, the BAS PLUS feature provides support. The required brake boosting effect for this is calculated according to the situation. This means that the brakes are automatically applied as intensively as required (max. approx. a = 10 m/s2 ). In doing this the threat of a collision can be reduced or at least the severity of the accident can be reduced.

If the driver does not react to the warning, the PRE-SAFE® brake function brakes the vehicle autonomously and can then mitigate the effects of a possible collision.

IMPORTANT The PRE-SAFE® brake function also supports the PRE-SAFE® safety concept.

The following partial functions of the DISTRONIC PLUS are described elsewhere:

The following graphics illustrate the function of the DISTRONIC PLUS incl. BAS PLUS and PRE-SAFE® brake.

G13845635Courtesy of MERCEDES-BENZ USA

Detection area of the radar sensor system 

Illustration of the principle of the functions BAS PLUS and PRE-SAFE® brake, shown on model 172 

G13845636Courtesy of MERCEDES-BENZ USA

Operation of the DISTRONIC PLUS takes place over the cruise control lever.

Design of the cruise control lever 

G13845637Courtesy of MERCEDES-BENZ USA

Operation over the CC lever, vehicle without code 494 (USA version)) 

G13845638Courtesy of MERCEDES-BENZ USA

Operation over CC lever, vehicle with code (494) USA version: 

G13845639Courtesy of MERCEDES-BENZ USA

IMPORTANT The distance to the vehicle driving immediately ahead is displayed in the multifunction display for t = 5 s after actuation of the CC lever Through selection of the operating level "DISTRONIC PLUS" in the. menu "Assistance" the distance graphic is shown permanently Display of the distance graphic can be switched on or off independently of the activity of the automatic distance control. The distance to the vehicle driving immediately ahead can be set over the DISTRONIC control in seven stages between t = 1.0 and 2.0 s. If a distance of t = 2.0 s is set for example the vehicle driving immediately ahead will be followed at a temporal distance of t = 2.0 s. The controlling takes place using the radar sensors control unit. The radar sensors control unit actively intervenes in the engine management as well as in the brake system to realize the functions. The optical and acoustic warnings are emitted by the IC. The radar sensor system control unit evaluates the input factors and transmits an appropriate request for controlling of the DISTRONIC PLUS BAS PLUS and PRE-SAFE® brake functions via the following CANs:

The radar sensors control unit evaluates the following input factors: 

Operating condition for engine/drivetrain:

The CDI control unit or the ME-SFI [ME] control unit sends the "Engine running" or the "Drivetrain operational" signal via the chassis CAN to the radar sensors control unit.

Engaged gear range (with transmission 722.9, 725.0):

The fully integrated transmission control unit sends the information on the engaged gear range via the drive train CAN, CDI control unit or ME-SFI control unit and chassis CAN to the radar sensors control unit.

Parking brake status:

The status of the parking brake (activated or deactivated) is sent by the electric parking brake control unit via the chassis CAN to the radar sensors control unit.

Engine drive torque:

The CDI control unit or ME-SFI [ME] control unit sends information about the currently available engine drive torque via the chassis CAN to the Electronic Stability Program control unit which evaluates this appropriately and transmits it via the chassis CAN to the radar sensors control unit.

Braking torque:

The Electronic Stability Program control unit transmits information about the currently applied braking torque via the chassis CAN to the radar sensors control unit.

Acceleration/yaw rate:

The acceleration/turn rate is detected by the yaw rate sensor for lateral and longitudinal acceleration. This transmits the corresponding data via the vehicle dynamics CAN to the Electronic Stability Program control unit and chassis CAN to the radar sensors control unit.

IMPORTANT On safety and comfort grounds the maximum (positive) acceleration of the automatic distance control is limited to about a = 2.5 m/s2 . It behaves in reverse proportion to the vehicle speed. This means that smaller accelerations are permitted for an increasing vehicle speed.

Driver request via the cruise control lever:

The driver request over the CC lever are directly read in by the steering column tube module control unit. The steering column tube module control unit transmits the control signals from the CC lever via the chassis CAN to the radar sensors control unit. The driver request "Overtake":

The steering column tube module control unit directly reads in the switch position of the combination switch and transmits it to the radar sensors control unit via the chassis CAN.

Driver request via menu settings in the IC:

The following settings can be selected over the menu settings in the IC:

The instrument cluster transmits the corresponding status via chassis CAN to the radar sensors control unit.

Vehicle speed/acceleration:

The vehicle speed is calculated on the basis of the wheel speeds. The acceleration is defined over the increase in rotational speed. The RPM sensors detect the wheel speeds. The Electronic Stability Program control unit directly reads in the signals from the RPM sensors and sends them via the chassis CAN to the radar sensors control unit. GPS signals:

The NAV in the COMAND controller unit or the radio, in combination with the navigation module connected via the telematics CAN, receives the GPS signals

The NAV transmits the GPS signals via the interior CAN, front SAM control unit and chassis CAN to the radar sensors control unit.

Steering wheel angle:

The steering angle is recorded by the steering wheel angle sensor. The steering column tube module control unit directly reads in the signals of the steering wheel angle sensor and sends information about the steering angle to the radar sensors control unit via the chassis CAN.

Object recognition in the short range:

The short range radar sensor system in the front bumper operates in the 24 GHz frequency range (up to 30.11.2012) or in the 25 GHz frequency range (as of 01.12.2012) for a maximum range of s = 30 m and is integrated into the following assembly parts:

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

The detection angle of the short range radar sensors is a maximum of ∠ = 130°. A precise angle can be determined within a detection zone of ∠ = 60° and up to ∠ = 130° only after detection of the objects. The radar sensors communicate via the sensor CAN with the radar sensors control unit. Object recognition in the long range:

The long range radar is integrated in the DISTRONIC controller unit and operates in the 77 GHz frequency range. With its detection angle of ∠ = 18° the long range radar covers the front area of the vehicle at a length of ∠ = 60 up to 200 m. The range ∠ = 0 m to s = 60 m in front of the vehicle is detected for an angle of ∠ = 60°. The DISTRONIC controller unit performs a soiling and function test to ensure proper operation after each engine start. The function test requires an object in the detection range of the long range radar which is used as a reference value for the function test by the DISTRONIC controller unit. DISTRONIC PLUS cannot be activated if a malfunction is established or if there are no objects (for the function test) in the detection range of the long range radar. The DISTRONIC PLUS controller unit communicates via the vehicle dynamics CAN with the radar sensors control unit.

Brake pedal position:

Operation of the brake pedal is registered by the brake lights switch. The Electronic Stability Program control unit directly reads in the status of the brake lights switch and transmits this to the radar sensors control unit via the chassis CAN.

Accelerator pedal position:

Operation of the accelerator pedal is registered by the accelerator pedal sensor. The CDI control unit or the ME-SFI [ME] control unit directly reads in the signals from the accelerator pedal sensor and transmits these to the radar sensors control unit via the chassis CAN.

The radar sensors control unit emits the following initial parameters (requests): 

Engage targeted gear:

The radar sensors control unit transmits the appropriate request via the chassis CAN to the Electronic Stability Program control unit. The Electronic Stability Program control unit evaluates this request as well as further driving dynamics requests internally and transmits them, according to requirements via chassis CAN, the CDI control unit or the ME-SFI [ME] control unit and drive train CAN to the fully integrated transmission control unit. This is however simply to be understood as a switching recommendation.

Downshifting or upshifting of the A/T takes place autonomously itself by the fully integrated transmission control unit, dependent on the current operating condition.

Raise/reduce engine torque:

The radar sensors control unit transmits the appropriate request via the chassis CAN to the Electronic Stability Program control unit. The Electronic Stability Program control unit evaluates this request as well as further driving dynamics requests internally and transmits a corresponding request via the chassis CAN to the CDI control unit or the ME-SFI [ME] control unit. The CDI control unit or the ME-SFI [ME] control unit implements this request.

Switch short range radar Off/On (until 30.11.2012): The radar sensors control unit switches the short range radar off and on again dependent on the protection zones around the radio astronomy stations. The short range radar can also be switched off and on again manually over the menu "Vehicle settings" in the IC. The radar sensors control unit transmits the appropriate request via the sensor CAN to the DISTRONIC (DTR) sensors on the front bumper.

IMPORTANT As of 01.12.2012 the radar sensor system will no longer be automatically deactivated. 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 blanked out. Thus operation of the radar sensor system within the protected areas of the radio astronomy stations is permissible. The radar sensor system can also no longer be switched off and on again manually.

Raise/reduce braking torque:

The radar sensors control unit transmits the appropriate request via the chassis CAN to the Electronic Stability Program control unit. The Electronic Stability Program control unit evaluates this request as well as further driving dynamics requests internally and actuates the traction system hydraulic unit accordingly. The braking torque is increased or reduced.

Emit warning tones, system messages or warnings:

The radar sensors control unit transmits the appropriate requests via the chassis CAN to the IC.

The DISTRONIC PLUS includes the following partial functions:

Additional function requirements for DISTRONIC PLUS 

IMPORTANT If the SPEEDTRONIC LED (without code 494 (USA version)) lights up, the DISTRONIC PLUS is deactivated and the function variable SPEEDTRONIC (without code 494 (USA version)) preselected.

Function sequence for DISTRONIC PLUS 

The description of the DISTRONIC PLUS function takes place, as an example, in the following chronological sequence:

The sequence can vary depending on the driver requests and the current traffic situation.

Activate DISTRONIC PLUS and drive off automatically 

The DISTRONIC PLUS can only be activated when stationary if there was also a stationary vehicle detected over the radar sensor system. This displayed by the distance graphic in the multifunction display. If the vehicle driving immediately ahead moves off, the driver can press the accelerator pedal to confirm the automatic drive off function or alternatively actuate the "Resume from memory" switch on the CC lever. The brake pedal must not be pressed during this time. The vehicle subsequently starts off automatically, accelerates and follows the vehicle driving immediately ahead at the programmed distance up to the maximum speed to be set.

Technical implementation 

To do this the radar sensors control unit receives or transmits the following information or requests:

Input factors:

Initial parameters:

Automatic distance control 

The automatic distance control can only be activated while driving (v < 30 km/h (mph)) if a vehicle driving immediately ahead was detected. If the vehicle driving immediately ahead brakes or accelerates, the DISTRONIC PLUS instigates the following measures for maintain the clearance:

The driver must press on the brake pedal if he sees that the instigated measures are not adequate to avoid a possible collision.

If the vehicle driving immediately ahead accelerates again, the engine torque is increased and the vehicle also accelerates.

The driver also has the option to accelerate the vehicle (e.g. to overtake a vehicle).

The automatic acceleration is put out of action for as long a the driver uses the accelerator pedal. The multifunction display shows the message "DISTRONIC passive".

If the automatic distance control requires a higher acceleration than the driver prescribes, the driver request is overlaid by the request for automatic distance control.

Technical implementation 

To do this the radar sensors control unit receives or transmits the following information or requests:

Input factors:

Initial parameters:

Change of driving lane (overtaking) 

For overtaking above a speed of v = 60 km/h (mph) the vehicle is also accelerated automatically. To do this the driver must initiate the overtaking maneuver by setting the turn signal.

In as far as the automatic distance control is activated, the radar sensors control unit recognizes the intention of the driver to overtake and accelerates the vehicle while taking account of the distance to the vehicle driving immediately ahead.

The vehicle then accelerates up to set maximum speed (automatic speed control) after the overtaking maneuver in as far as there was no vehicle driving immediately ahead detected as a target object.

If a vehicle driving immediately ahead is subsequently detected as a target object the automatic speed control function changes over again into the automatic distance control function.

The overtaking maneuver is broken off in the following situations:

Technical implementation 

To do this the radar sensors control unit receives or transmits the following information or requests:

Input factors:

Initial parameters:

Automatic speed control 

If the vehicle is in active distance control and the vehicle driving in front accelerates above v = 200 km/h or removes itself from the detection area of the radar sensor system, the automatic distance control function switches over to the automatic speed control function.

IMPORTANT The automatic speed control is described elsewhere.

Technical implementation 

To do this the radar sensors control unit receives or transmits the following information or requests: Input factors:

Initial parameters:

Passing through a radio astronomy protection zone 

For vehicles up to 30.11.2012, the short range radar sensor system is automatically switched off in certain protected areas around radio astronomy stations as a result of legal requirements on the 24 GHz radar system (short range radar, band width: f = 5 GHz) in Western Europe.

When DISTRONIC PLUS is active, the message "Radar sensor system automatically switched off, see operator's manual" is shown on the multifunction display of the instrument cluster.

When the vehicle leaves the protected area, the short range radar sensor system is switched on again automatically.

For an activated DISTRONIC PLUS the message "DISTRONIC PLUS available again" is issued.

IMPORTANT As of 01.12.2012 the radar sensor system will no longer be automatically deactivated. 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 blanked out. Thus operation of the radar sensor system within the protected areas of the radio astronomy stations is permissible. It is therefore also no longer necessary to have localization of the vehicle over GPS.

IMPORTANT For vehicles up to 30.11.2012 the driver has the option to manually switch the short range radar sensors on and off over the "Vehicle settings" in the IC. If one seeks to manually switch on the short range radar sensors within a protected area, the message "Radar sensor system switched off automatically" is displayed in the multifunction display.

Technical implementation (up to 30.11.2012) 

The protected areas of the radio astronomy stations are stored in the form of Global Positioning System (GPS) coordinates in the radar sensors control unit. The radar sensors control unit evaluates the GPS signals and switches the short range radar sensors off if necessary. To do this the radar sensors control unit receives or transmits the following information or requests: Input factors:

Initial parameters:

Passing over round about, T intersections and freeway exit lane 

The DISTRONIC PLUS function uses navigation data to adapt the system behavior to the following situations:

This means that if the vehicle driving immediately ahead leaves the detection area of the radar sensor system in one of the above-mentioned traffic situations then the current speed is maintained:

If no vehicle driving immediately ahead is detected afterwards, the vehicle accelerates or decelerates to the set specified speed.

IMPORTANT Since traffic situations are subject to alteration, the digital map data has to be regularly updated.

Technical implementation 

To do this the radar sensors control unit receives or transmits the following information or requests:

Input factors:

Initial parameters:

Going back into a lane/person in the front regulation 

If the vehicle driving immediately ahead turns off and there is another vehicle in front, the system only switches over to the new target vehicle if it is moving. The system does not operate for stationary objects unless a preceding vehicle is tracked to a standstill.

If while driving a vehicle turns in front within the safe distance to the vehicle driving immediately ahead, the distance to this new vehicle is regulated.

If the vehicle is in automatic speed control and a vehicle tuns onto the lane driven in this vehicle is registered as the vehicle driving immediately ahead.

If the distance to the moving in vehicle is below the value which was programmed, the DISTRONIC PLUS function brakes the vehicle. If the requested brake power is not adequate the driver must press the brake pedal.

IMPORTANT The negative acceleration (deceleration) over the traction system hydraulic unit is limited to 40% (about a = 4 m/s2 ) of the maximum possible brake power.

DISTRONIC PLUS is thereby deactivated

This process is signaled to the driver by outputting of a notification tone over the warning buzzer and indication of a message in the multifunction display.

The driver can subsequently reactivate the DISTRONIC PLUS

Technical implementation 

To do this the radar sensors control unit receives or transmits the following information or requests:

Input factors:

Initial parameters:

Automated Stop Vehicle 

For an active DISTRONIC PLUS the vehicle will follow the vehicle driving immediately ahead to standstill.

Of the vehicle is stationary it is secured against rolling away through activation of the service brake (safety strategy of standstill control).

IMPORTANT Securing the vehicle using the DISTRONIC PLUS function (standstill control) does not replace securing the vehicle for parking.

Technical implementation 

To do this the radar sensors control unit receives or transmits the following information or requests: Input factors:

Initial parameters:

The following traffic situations show the limits of the DISTRONIC PLUS.

Obstacles and stationary vehicles 

G07300324Courtesy of MERCEDES-BENZ USA

The DISTRONIC PLUS does not brake for obstacles or stationary vehicles which were not previously registered as the target object.

If for example the detected vehicle turns off and there is an obstacle or a stationary vehicle behind it no automatic intervention by the brake system occurs.

Curves, curved entrances and exits 

G07300325Courtesy of MERCEDES-BENZ USA

The DISTRONIC PLUS can only provides limited detection of vehicles in curves. The vehicle can then brake unexpectedly or late.

Vehicles moving across in front of one's own vehicle 

G07300326Courtesy of MERCEDES-BENZ USA

DISTRONIC PLUS may detect vehicles in cross traffic by mistake.

For an activated distance control the vehicle can start off unintended, (e g. at a traffic light with cross-traffic).

Offset driving style 

G10050075Courtesy of MERCEDES-BENZ USA

DISTRONIC PLUS may not be able to detect vehicles driving displaced to one side. The distance to the vehicle in front becomes too small.

Lane change by other vehicles 

G10050076Courtesy of MERCEDES-BENZ USA

The DISTRONIC PLUS does not yet detect the vehicle moving into the lane. The distance to the vehicle moving into the lane becomes too small.

Narrow vehicles 

G10050077Courtesy of MERCEDES-BENZ USA

The DISTRONIC PLUS does not recognize the vehicle driving immediately ahead on the driving lane because it is too small. The distance to the vehicle in front becomes too small.

Function sequence for PRE-SAFE® brake and BAS PLUS 

The BAS PLUS and the PRE-SAFE® brake functions assess the traffic situation in front of the vehicle.

In the following vehicle speed ranges emergency braking by the driver is supported by the function BAS PLUS or the vehicle is braked automatically in dangerous situations by the function PRE-SAFE® brake:

In the case of stationary obstacles, the BAS PLUS function or the PRE-SAFE® brake function is only activated if the vehicle's own vehicle speed is a maximum of v = 72 km/h.

If a stationary object is detected in the lane by both the short and long range radar sensor systems (the lane is determined, amongst other things, by the steering wheel angle and vehicle speed, etc.), the BAS PLUS function and the PRE-SAFE® brake function are activated. The description of the PRE-SAFE® brake function and the BAS PLUS is subdivided as follows:

BAS PLUS 

If the driver then reacts to the collision-critical distance warning with an emergency braking maneuver, the BAS PLUS function provides support for optimum utilization of the braking distance to the obstacle. If there is no actuation by the driver of the brake pedal or the intensity of actuation of the brake pedal reduces, the brake boosting effect is reduced to the driver braking level and the BAS PLUS function is deactivated. The function BAS PLUS will also be deactivated if the driver presses on the accelerator pedal.

Technical implementation 

The emergency braking is defined over the actuation speed and the actuation strength with which the brake pedal is actuated.

To do this the radar sensors control unit also uses data from the radar sensor system and calculates the necessary brake servo assistance while taking account of the distance and the closing speed to the obstacle.

IMPORTANT Parallel to this the function PRE-SAFE® integrated into the Electronic Stability Program control unit evaluates the current requested braking torque and instigates appropriate measures as necessary.

To do this the radar sensors control unit receives or transmits the following information or requests: Input factors:

Initial parameters:

PRE-SAFE® brake 

The PRE-SAFE® brake function includes a distance warning function to warn the driver of moving or stationary obstacles in his lane. The distance warning occurs in a vehicle speed range of v = 7 to 250 km/h.

In this case differentiation is made between a static distance warning and a collision critical distance warning.

Static distance warning:

The static distance warning is triggered if the time interval between the system vehicle and vehicle driving immediately ahead is less than t = 0.8 s (ie in moving traffic) The DISTRONIC warning lamp lights up in the IC.

Collision critical distance warning:

If a moving obstacle in the detection range of the radar sensor system is classified as representing a critical accident situation (a collision within t < 2.6 s) the DISTRONIC warning lamp lights up and the warning buzzer emits an intermittent tone.

The warning output is automatically switched off again when the situation is no longer critical and cannot be acknowledged during an active control.

IMPORTANT The distance warning function can be activated and deactivated separately and independently of the automatic distance control in the menu "PRE-SAFE® brake" of the instrument cluster.

The distance warning is basically active for an active DISTRONIC PLUS. If the DISTRONIC PLUS is deactivated actuation of the DISTRONIC warning lamp takes place by the function PRE-SAFE® brake.

Optical warning messages in instrument cluster when a safe distance is not maintained 

G13845646Courtesy of MERCEDES-BENZ USA

If the driver does not react to the warning signals the PRE-SAFE® brake function initiates partial braking.

If the driver does not react to the partial braking and if the radar sensors control unit calculates that the collision with the obstacle is unavoidable the radar sensors control unit instigates emergency braking for t = 1 s and thus reduces the possible consequences of an accident.

IMPORTANT Emergency braking is not triggered if the front passenger seat is occupied and the front passenger is not strapped in.

To do this the video and radar sensors control unit calculates a braking torque while taking account of the driving dynamics input factors.

The vehicle is braked according to this request.

Technical implementation 

To do this the radar sensors control unit receives or transmits the following information or requests:

Input factors:

Initial parameters:

  Electrical function schematic for DISTRONIC PLUS incl. BAS PLUS and PRE-SAFE brake   PE30.30-P-2055-97TAA 
  Overview of system components for driver assistance systems   GF54.00-P-9998RD
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