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

Model 172.4 

up to model year 2017 

Shown on model 172.4 

G13845630Courtesy of MERCEDES-BENZ USA

Cruise control function requirements 

Cruise control - general 

The CC function automatically regulates the vehicle speed as constant at the speed specified by the driver.

To do this the CC function evaluates the operator requests of the driver and the current driving condition.

The CC function is implemented dependent on the model and the equipment by the following control unit:

For vehicles with code 233 (DISTRONIC PLUS) the radar sensors control unit (until 31.05.2015) transmits function relevant requests via the chassis CAN to the Electronic Stability Program control unit. The Electronic Stability Program control unit receives and processes these and prioritizes them according to the respective own evaluated parameters.

Operation of the CC function 

G13845631Courtesy of MERCEDES-BENZ USA

The CC function can be activated over the following controls:

This sets the current vehicle speed as the target speed.

IMPORTANT If a target speed was already set since the last engine start this can be called up by actuating the switch Resume from memory. The vehicle accelerates or decelerates to the last selected target speed.

Using the switches "decelerate" and "set" and the switches "accelerate" and "set", the target speed can be altered in steps of v = 1 km/h or v = 10 km/h.

Actuation up to the actuation point increases the set speed by v = 1 km/h.

If the switch is pressed beyond the actuation point then the set speed increases each time by v = 10 km/h.

If the switch is held at or beyond the over-center preload the set speed is altered every t = 0.6 s.

The following input factors are evaluated to implement the CC function: 

Operating condition for engine/drivetrain:

The CDI control unit or the ME-SFI [ME] control unit transmits the signal "Engine running" or "Drivetrain operational" via the chassis CAN to the Electronic Stability Program control unit and, for vehicles with code 233 (DISTRONIC PLUS), also to the radar sensors control unit (until 31.05.2015). Vehicle speed:

The vehicle speed is calculated on the basis of the wheel speeds. 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 for vehicles with code 233 (DISTRONIC PLUS) via chassis CAN to the radar sensors control unit (until 31.05.2015).

Engaged gear range (transmission 722.9, 725.0):

Information about the engaged gear range is sent by the fully integrated transmission control unit via the drive train CAN, CDI control unit or ME-SFI [ME] control unit and chassis CAN to the Electronic Stability Program control unit and, for vehicles with code 233 (DISTRONIC PLUS), also to the radar sensors control unit (until 31.05.2015).

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 of the CC lever via the chassis CAN to the Electronic Stability Program control unit and, for vehicles with code 233 (DISTRONIC PLUS), also to the radar sensors control unit (until 31.05.2015).

Accelerator pedal position:

Operation of the accelerator pedal is registered by the accelerator pedal sensor.

The CDI control unit or the ME-SFI [ME] directly reads in the signals from the accelerator pedal sensor and sends them via the chassis CAN to the Electronic Stability Program control unit and also for vehicles with code 233 (DISTRONIC PLUS) to the radar sensors control unit (until 31.05.2015).

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

The Electronic Stability Program control unit evaluates the input factors as well as further driving dynamics requests and transmits the request "increase/reduce engine torque" 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.

For vehicles with code 233 (DISTRONIC PLUS), the radar sensors control unit (until 31.05.2015) transmits the "Increase/reduce engine torque" request via the chassis CAN to the Electronic Stability Program control unit.

Engage targeted gear (transmission 722.9, 725.0):

The Electronic Stability Program control unit evaluates the input factors as well as further driving dynamics requests and sends the request "Engage targeted gear" via chassis CAN, CDI control unit or ME-SFI [ME] control unit and drive train CAN to the fully integrated transmission control unit.

For vehicles with code 233 (DISTRONIC PLUS) the radar sensors control unit (until 31.05.2015) transmits the request "Engage targeted gear" via the chassis CAN to the Electronic Stability Program control unit.

This request is however 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 braking torque:

The Electronic Stability Program control unit evaluates the input factors and actuates the traction system hydraulic unit appropriately. The traction system hydraulic unit reacts by increasing or reducing the braking torque.

For vehicles with code 233 (DISTRONIC PLUS), the radar sensors control unit (until 31.05.2015) transmits the "Increase/reduce braking torque" request via the chassis CAN to the Electronic Stability Program control unit.

The cruise control function includes 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 set speed is displayed in the speedometer.

The Electronic Stability Program control unit transmits the appropriate information via the chassis CAN to the IC.

For vehicles with code 233 (DISTRONIC PLUS) the radar sensors control unit (until 31.05.2015) transmits the respective information via the chassis CAN to the IC.

The following events deactivate the automatic speed control:

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

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 target speed is regulated again after removal of the acceleration request (releasing the accelerator pedal).

Function sequence for SPEEDTRONIC 

The SPEEDTRONIC encompasses the following subfunctions:

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

IMPORTANT Kickdown: accelerator pedal pressed by > 90% and vehicle speed v < 20 km/h less than the selected maximum speed.

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

The maximum speed of the vehicle can be limited at any time to a freely selectable value (e.g. 50 km/h in urban traffic) over the variable SPEEDTRONIC.

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 km/h to 240 km/h.

Adjustment of the maximum speed takes place in the menu "Settings", "Vehicle" and "Limitation (winter tires)" in the instrument cluster. The IC transmits the set maximum speed via the chassis CAN to the Electronic Stability Program control unit.

For vehicles with code 233 (DISTRONIC PLUS) the IC (until 31.05.2015) transmits the maximum speed via the chassis CAN to the radar sensors control unit.

Approximately v = 10 km/h before reaching the set maximum speed, a message appears in the multifunction display that indicates a maximum speed limitation. To do this the Electronic Stability Program control unit transmits the appropriate request via the chassis CAN to the IC.

The driver can accelerate the vehicle up to the set maximum speed. If the maximum speed was reached the following activities are started:

  Electrical function schematic for cruise control (CC) Model 172.4 as of model year 2016 up to model year 2017 with code 239 (DISTRONIC PLUS) PE30.30-P-2051-97TAC 
  Model 172.4 up to model year 2017/except code 233 (DISTRONIC PLUS) except code 239 (DISTRONIC PLUS} PE30.30-P-2051-97TAA
  Model 172.4 up to model year 2016 with code 233 (DISTRONIC PLUS) PE30.30-P-2051-97TAB 
  Overview of system components for driver assistance systems   GF54.00-P-9998RD
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