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Cruise Control (CC), Function - GF30.30-P-0001RF

Model 205 

up to model year 2019 

Model 253 (except 253.99) 

up to model year 2020 

G12935928Courtesy of MERCEDES-BENZ USA

Function requirements, general 

CC operation 

G12935929Courtesy of MERCEDES-BENZ USA

The cruise control is activated using the resume from memory switch. Here the last stored or momentary vehicle speed is set as the set speed. The specified speed can be changed in steps of v = 1 km/h or v = 10 km/h using the decelerate and set switch and the accelerate and set switch.

Cruise control - general 

The cruise control regulates the vehicle speed constantly and automatically to the desired speed set by the driver. To do this, the cruise control evaluates the driver's commands and the current driving condition.

Function-related requests are transmitted via suspension FlexRay to the Electronic Stability Program control unit by the DISTRONIC electric controller unit for vehicles with code 239 (Active Distance Assist DISTRONIC) or by the radar sensors control unit for vehicles with code 266 (DISTRONIC PLUS with Steering Assist and Stop & Go Pilot). The Electronic Stability Program control unit processes these and prioritizes them according to the respective own evaluated parameters.

Upon actuation up to the actuation point, the specified speed is changed by v = 1 km/h. Upon actuation past the actuation point, the specified speed is changed by v = 10 km/h in each case. If the switch is held at or beyond the actuation point, the specified speed is changed every t = 0.6 s.

The following input factors are evaluated to implement the function: 

Operating condition for engine/drivetrain:

The CDI control unit or the ME-SFI control unit transmits the "Engine running" or "Drivetrain operational" signal via drive CAN, powertrain control unit and suspension FlexRay to the Electronic Stability Program control unit and for vehicles with CODE 239 (Active Distance Assist DISTRONIC) also to the DISTRONIC electric controller unit or for vehicles with Code 266 (DISTRONIC PLUS with Steering Assist and Stop & Go Pilot) to the radar sensors control unit.

IMPORTANT The CDI control unit or the ME-SFI [ME] control unit, amongst other things, coordinates acceleration, deceleration or switching requirements. In doing so it prioritizes requests according to their relevance, while taking account of the additional variables such as the charge level of the high voltage on-board electrical system, the operating condition of the ancillaries or requests from the comfort systems such as the AAC. Engaged gear range:

With transmission 722, 724, 725, the fully integrated transmission control unit transmits information on the engaged drive range via the drive CAN, powertrain control unit and suspension FlexRay to the Electronic Stability Program control unit, and for vehicles with code 239 (Active Distance Assist DISTRONIC), the information is also transmitted to the DISTRONIC electric controller unit, or for vehicles with code 266 (DISTRONIC PLUS with Steering Assist and Stop & Go Pilot) it is transmitted to the radar sensors control unit.

Vehicle speed:

The vehicle speed is calculated from the wheel speed signals. The Electronic Stability Program control unit directly reads in the signals from the rpm sensors.

For vehicles with code 239 (Active Distance Assist DISTRONIC), the Electronic Stability Program control unit also transmits the wheel speed signals via suspension FlexRay to the DISTRONIC electric controller unit.

For vehicles with code 266 (DISTRONIC PLUS with Steer Assist and Stop & Go Pilot), the Electronic Stability Program control unit transmits wheel speed signals via the chassis FlexRay to the radar sensors control unit.

Driver request via the cruise control lever:

The steering column tube module control unit directly reads in the driver requests via the cruise control lever and sends them via suspension FlexRay to the Electronic Stability Program control unit and, for vehicles with code 239 (Active Distance Assist DISTRONIC), additionally transmits them to the DISTRONIC electric controller unit or, for vehicles with code 266 (DISTRONIC PLUS with Steering Assist and Stop & Go Pilot), transmits them to the radar sensors control unit.

Accelerator pedal position:

The CDI control unit or the ME-SFI control unit transmits information about the accelerator pedal position via the drive CAN, powertrain control unit, and suspension FlexRay to the Electronic Stability Program control unit and, for vehicles with code 239 (Active Distance Assist DISTRONIC), additionally transmits them to the DISTRONIC electric controller unit or, for vehicles with code 266 (DISTRONIC PLUS with Steering Assist and Stop & Go Pilot), transmits them to the radar sensors control unit.

The following initial parameters (requests) are issued to implement the function: 

Raise/reduce engine torque:

For vehicles except code 239 (Active Distance Assist DISTRONIC) and except code 266 (DISTRONIC PLUS with Steering Assist and Stop & Go Pilot), the Electronic Stability Program control unit transmits the request "raise engine torque" or "reduce engine torque" via suspension FlexRay, powertrain control unit, and engine CAN to the CDI control unit or ME-SFI control unit.

For vehicles with code 239 (Active Distance Assist DISTRONIC), the DISTRONIC electric controller unit or, for vehicles with code 266 (DISTRONIC PLUS with Steering Assist and Stop & Go Pilot), the radar sensors control unit transmits the request "raise engine torque" or "reduce engine torque" via suspension FlexRay to the Electronic Stability Program control unit. The Electronic Stability Program control unit processes this and transmits it according to its priority via the chassis FlexRay, powertrain control unit and engine 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.

Engage targeted gear (downshift or upshift) (transmission 722, 724, 725):

For vehicles except code 239 (Active Distance Assist DISTRONIC) and except code 266 (DISTRONIC PLUS with Steering Assist and Stop & Go Pilot), the Electronic Stability Program control unit evaluates the input factors and other driving dynamic requests and transmits the "engage requested gear" request via suspension FlexRay, the powertrain control unit, and drive CAN to the fully integrated transmission control unit.

The "Engage requested gear" request is transmitted via suspension FlexRay to the Electronic Stability Program control unit by the DISTRONIC electric controller unit for vehicles with CODE 239 (Active Distance Assist DISTRONIC) or by the radar sensors control unit for vehicles with CODE 266 (DISTRONIC PLUS with Steering Assist and Stop & Go Pilot). The Electronic Stability Program control unit processes this and transmits it according to its priority via the chassis FlexRay, powertrain control unit and drive train CAN to the fully integrated transmission control unit.

This request is to be understood as a shift recommendation. Downshifting or upshifting of the automatic transmission takes place autonomously by the fully integrated transmission control unit dependent on the current operating condition.

Raise/reduce braking torque:

For vehicles except code 239 (Active Distance Assist DISTRONIC) and except code 266 (DISTRONIC PLUS with Steering Assist and Stop & Go Pilot), the Electronic Stability Program control unit evaluates the input factors and actuates the traction system hydraulic unit.

For vehicles with code 239 (Active Distance Assist DISTRONIC), the DISTRONIC electric controller unit or for vehicles with code 266 (DISTRONIC PLUS with Steering Assist and Stop & Go Pilot), the radar sensors control unit transmits the "raise braking torque" or "reduce braking torque" request via suspension FlexRay to the Electronic Stability Program control unit. The Electronic Stability Program control unit evaluates these and actuates the traction system hydraulic unit appropriately.

The traction system hydraulic unit reacts by increasing or reducing the braking torque.

IMPORTANT Model 205.012/047/147/212/247

up to model year 2019

Model 253.354/954

up to model year 2020

For model the kinetic energy is converted within defined limits into electrical energy (regenerative braking). If the required braking torque exceeds the deceleration through regenerative braking, the regenerative braking system control unit also actuates Electronic Stability Program control unit and the traction system hydraulic unit and therefore the service brake.

Cruise control encompasses the following subfunctions:

Additional automatic speed control function requirements 

Function sequence for automatic speed control 

Through actuation of the "Resume from memory" switch the last set speed stored is applied, provided a set speed was stored since the last engine start. If no set speed was stored, the current vehicle speed is set as the set speed. The target speed is displayed in the multifunction display of the instrument cluster.

For vehicles except code 239 (Active Distance Assist DISTRONIC) and except code 266 (DISTRONIC PLUS with Steering Assist and Stop & Go Pilot), the Electronic Stability Program control unit transmits the speed setting (specified speed) via suspension FlexRay, electronic ignition lock control unit and user interface CAN to the instrument cluster.

The set speed (specified speed) is transmitted to the instrument cluster via suspension FlexRay, electronic ignition lock control unit and user interface CAN by the DISTRONIC electric controller unit for vehicles with CODE 239 (Active Distance Assist DISTRONIC) or by the radar sensors control unit for vehicles with CODE 266 (DISTRONIC PLUS with Steering Assist and Stop & Go Pilot).

IMPORTANT The driver also has the option to accelerate beyond the set target speed through actuation of the accelerator pedal (for example when overtaking). The set speed is regulated again after removal of the acceleration request (releasing the accelerator pedal).

The following activities are started in order to reach or maintain the set speed:

The following events deactivate the automatic speed control:

Function sequence for SPEEDTRONIC 

The SPEEDTRONIC comprises the following subfunctions:

Additional function requirements for variable SPEEDTRONIC (without code 494 (USA version)) 

Function sequence for variable SPEEDTRONIC (except code 494 (USA version)) 

The variable SPEEDTRONIC can be used to limit the maximum design speed of the vehicle to a freely selectable value (e.g. v = 50 km/h in urban traffic). The driver can accelerate the vehicle up to the set limit. If the set limit was reached, the following activities are started:

IMPORTANT If switching takes place on the variable SPEEDTRONIC on the CC lever, the automatic speed control is deactivated.

The following events deactivate the variable SPEEDTRONIC:

Function sequence for permanent limiter 

The maximum speed of the vehicle can be limited in steps of v = 10 km/h from v = 160 to 240 km/h. The maximum speed is set in the "Settings", "Vehicle" and "Limitation (winter tires)" menu in the instrument cluster. For vehicles except code 239 (Active Distance Assist DISTRONIC) and except Code 266 (DISTRONIC PLUS with Steering Assist and Stop & Go Pilot), the instrument cluster transmits the set maximum speed via the user interface CAN, electronic ignition lock control unit, and suspension FlexRay to the Electronic Stability Program control unit. For vehicles with code 239 (Active Distance Assist DISTRONIC), the instrument cluster transmits the set maximum speed via the user interface CAN, electronic ignition lock control unit, and suspension FlexRay to the DISTRONIC electric controller unit.

In vehicles with code 266 (DISTRONIC PLUS with Steering Assist and Stop & Go Pilot), the instrument cluster transmits the selected maximum speed via the user interface CAN, electronic ignition lock control unit and suspension FlexRay to the radar sensors control unit.

Approx. v = 10 km/h before reaching the selected maximum speed, a message appears in the multifunction display of the instrument cluster, which indicates the maximum speed limitation. The driver can accelerate the vehicle up to the set maximum speed.

When the selected maximum speed is reached, the following activities are started:

  Electrical function schematic for cruise control (CC) Model 205 up to model year 2019 except code 239 (Active Distance Assist DISTRONIC) except code 266 (DISTRONIC PLUS with Steer Assist and Stop & Go Pilot) Model 253 (except 253.99) up to model year 2020 except code 239 (Active Distance Assist DISTRONIC) except code 266 (DISTRONIC PLUS with Steer Assist and Stop & Go Pilot) PE30.30-P-2051-97FBA 
  Electrical function schematic for cruise control
(CC)		 Model 205 up to model year 2019 with code 239 (Active Distance Assist DISTRONIC) Model 205 up to model year 2019 with code 266 (DISTRONIC PLUS with Steer Assist and Stop & Go Pilot) Model 253 (except 253.99) up to model year 2020 with code 239 (Active Distance Assist DISTRONIC) Model 253 (except 253.99) up to model year 2020 with code 266 (DISTRONIC PLUS with Steer Assist and Stop & Go Pilot) PE30.30-P-2051-97FBB 
  Overview of system components for driver assistance systems   GF54.00-P-9998RF
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