Cruise control (CC), function - GF30.30-P-0001CE

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MODEL 204 with CODE (440) Cruise control as of model year 2009

/YoM 08

MODEL 204.0/2 with CODE (233) Distronic Plus with CODE (237) Active Blind Spot Assist with CODE (238) Active Lane Keeping Assist as of model year 2012

/YoM 11 facelift

MODEL 204.3 with CODE (233) Distronic Plus with CODE (237) Active Blind Spot Assist with CODE (238) Active Lane Keeping Assist

Fig 1: Identifying Cruise Control (CC) Function Diagram

Courtesy of MERCEDES-BENZ USA

Function requirements, general

Circuit 61 ON or "PT_Rdy" (drivetrain ready) signal set
Vehicle speed v ≥30 up to 250 km/h (without code (494) USA version)
Vehicle speed v ≥20 up to 150 mph (for code (494) USA version)
Drive position "D" engaged (for transmission 722)

The circuit 61 status ON or the "PT_Rdy" signal is sent by the CDI control unit or the ME-SFI [ME] control unit via the chassis CAN.

Cruise control - general

The speed based function CC belongs to the driver assistance system and is integrated according to the installed equipment in the following control unit:

Electronic Stability Program control unit (without code (233) DISTRONIC PLUS and without code (237) Active Blind Spot Assist or without code (238) Active Lane Keeping Assist)
Video and radar sensor system control unit (with code (233) DISTRONIC PLUS, code (237) Active Blind Spot Assist or code (238) Active Lane Keeping Assist)

The CC constantly controls the actual speed of the vehicle without operation of the accelerator pedal to the target speed set by the driver. The vehicle is also automatically braked when driving down a hill to maintain the target speed through interventions in the service brakes.

The functionalities listed are regulated by means of a comparison between the specifications made by the driver and the actual value of the vehicle. The functionality is identical for all vehicle models and packages. Differentiation takes place by the control unit which

The function CC also includes the following functionalities:

Variable SPEEDTRONIC (without code (494) USA version): The variable SPEEDTRONIC allows the driver to set an individual maximum speed in the range v = 30 km/h up to the maximum vehicle speed.
Permanent limiter:

The permanent limiter allows the driver to permanently limit the maximum speed of the vehicle. This additional function is suitable for example for seasonal events such as operation of the vehicle with winter tires where the speed rating is below the maximum possible speed of the vehicle.

includes the CC function.

To do this the respective control unit determines and analyzes the following input factors:

Vehicle speed
Control signals from the CC lever
Status of accelerator pedal

Vehicle speed:

The Electronic Stability Program control unit reads in signals from the following components directly for computation of the vehicle speed:

Left front axle speed sensor
Right front axle speed sensor
Left rear axle speed sensor
Right rear axle speed sensor

For vehicles without code (233) DISTRONIC PLUS and without code (237) Active Blind Spot Assist or without code (238) Active Lane Keeping Assist, the vehicle speed is calculated in the Electronic Stability Program control unit.

For vehicles with code (233) DISTRONIC PLUS, code (237) Active Blind Spot Assist or code (238) Active Lane Keeping Assist, the Electronic Stability Program control unit transmits the wheel speeds via the chassis CAN to the video and radar sensor system control unit, which calculates the current speed.

Cruise control lever control signals:

The control signals from the following components are directly read in by the steering column tube module control unit:

Resume from memory switch (S40/4s1)
Decelerate and set switch (S40/4s2)
Accelerate and set switch (S40/4s3)
OFF switch (S40/4s4)

The steering column tube module control unit transmits the control signals via chassis CAN which are received according to the model and installed equipment by the following control unit:

Electronic Stability Program control unit or
Video and radar sensor system control unit

Status of accelerator pedal

The status of the accelerator pedal registers the accelerator pedal sensor which is read in directly by the CDI control unit or the ME-SFI [ME] control unit. The control unit or the ME-SFI [ME] control unit transmits signals from the accelerator pedal sensor via the chassis CAN according to the installed equipment to the following control unit:

Electronic Stability Program control unit or
Video and radar sensor system control unit

Operation:

The function cruise control and variable SPEEDTRONIC (without code (494) USA version) is operated over the cruise control lever. Selection of the speed takes place over the controls of the cruise control lever which are shown graphically below:

Design of the CC lever

Fig 2: Identifying Design Of CC Lever

Courtesy of MERCEDES-BENZ USA

All of the speed information listed below in mph refers to vehicles with code (494) USA version.

Function sequence for cruise control

The cruise control function is divided into the following subfunctions:

The desired specified speed can be set in v = 1 km/h (1 mph-) or v = 10 km/h (5 mph) steps using the following controls:

Resume from memory switch
Decelerate and set switch
Accelerate and set switch

Actuation of the switches listed up to the actuation point increases the set speed by v = 1 km/h (1 mph).

If the respective switch is actuated via the actuation point then the set speed increases each time by v = 10 km/h (5 mph).

If the respective switch is held at or beyond the actuation point then the set speed increases automatically by an interval of t = 0.6 s.

Function sequence for automatic speed control
Function sequence for SPEEDTRONIC

Additional automatic speed control function requirements

Cruise control selected with SPEEDTRONIC switch (without code (494) USA version) (SPEEDTRONIC LED not illuminated)
Electronic Stability Program (ESP) not passively switched (without model 204.077/277/375)
ESP not switched into "SPORT HANDLING MODE" (for model 204.077/277/375.)

Function sequence for automatic speed control

Through operation of the switch "resume fro memory switch", the last stored specified speed is set in as far as a specified speed was stored in the Electronic Stability Program control unit or the video and radar sensor system control unit since the last engine start. If no specified speed has been stored, the cruise control sets the current vehicle speed as the specified speed.

View of the IC for an active automatic speed control

Fig 3: Identifying View Of IC For Active Automatic Speed Control

Courtesy of MERCEDES-BENZ USA

If the automatic speed control is activated, the segments in the speedometer are illuminated from the specified speed to the end of the tachometer scale.

The following events lead to deactivation of the automatic speed control:

Operation of the OFF switch
Actuation of brake pedal
Active regulation of the ESP
Speed v < 25 km/h or v < 17 mph
Electric parking brake activated
Gear range not "D"

Function for vehicles without code (233) DISTRONIC PLUS and without code (237) Active Blind Spot Assist or without code (238) Active Lane Keeping Assist:

If the vehicle reaches the set specified speed, the engine power is reduced automatically.

To do this, the electronic stability program control unit sends a request to reduce the engine torque via the chassis CAN to the CDI control unit or the ME-SFI [ME] control unit.

The set specified speed is transmitted from the Electronic Stability Program control unit or the video and radar sensor system control unit via the chassis CAN to the IC for presentation in the speedometer of the IC.

If the actual speed drops below the speed set by the driver, the torque is increased accordingly.

If the vehicle reaches the specified speed set by the driver in decel mode, for example by driving down a hill, then the service brake is actuated in a metered fashion over the traction system hydraulic unit by the ESP control unit. For vehicles with transmission 722, the A/T is downshifted is also necessary according to the operating condition to reduce the load on the service brake system.

Downshifting of the A/T by the A/T takes place independently which means that the Electronic Stability Program control unit only transmits information about the necessity for a shift via the chassis CAN to the CDI control unit or the ME-SFI [ME] control unit which also, at the same time, includes limitation of the shift.

The CDI control unit or the ME-SFI [ME] control unit passes on the respective information or the request via the drive train CAN to the electronic transmission control unit (for transmission 722.6) or to the fully integrated transmission control unit (for transmission 722.9) which implements this appropriately.

To do this the video and radar sensor system control unit transmits a request to decrease the engine torque to the ESP control unit via the chassis CAN which evaluates this request as well as further driving dynamic requests internally and passes on their relevance

The driver also has the option to accelerate beyond the set target speed through actuation of the accelerator pedal (e.g. when overtaking). After release of the accelerator pedal, the cruise control regulates to reach the set target speed again.

Function for vehicles with code (233) DISTRONIC PLUS, code (237) Active Blind Spot Assist or code (238) Active Lane Keeping Assist: If the vehicle reaches the set specified speed, the engine power is reduced automatically.

appropriately to the CDI control unit or the ME-SFI [ME] control unit via the chassis CAN.

If the actual speed drops below the speed set by the driver, the torque is increased accordingly.

If the vehicle reaches the specified speed set by the driver in decal mode, for example by driving down a hill, then the service brake is actuated in a metered fashion over the traction system hydraulic unit by the ESP control unit.

To do this, the video and radar sensor system control unit sends a corresponding request, via the vehicle dynamics CAN, to the electronic stability program control unit.

For vehicles with transmission 722, the A/T is downshifted is also necessary according to the operating condition to reduce the load on the service brake system.

Downshifting of the A/T by the A/T takes place independently which means that the video and radar sensor system control unit only transmits information about the necessity for a shift via the chassis CAN to the CDI control unit or the ME-SFI [ME] control unit which also, at the same time, includes limitation of the shift.

The driver also has the option to accelerate beyond the set target speed through actuation of the accelerator pedal (e.g. when overtaking).

After release of the accelerator pedal, the cruise control regulates to reach the set target speed again.

Function sequence for SPEEDTRONIC

The partial function SPEEDTRONIC is subdivided into the following subfunctions:

D Function sequence for variable SPEEDTRONIC (without code (494) USA version)

D Function sequence for permanent limiter

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

Variable SPEEDTRONIC selected with SPEEDTRONIC switch (SPEEDTRONIC LED illuminated)
ESP not passively engaged (without model 204.077/277/375)
ESP not switched into "SPORT HANDLING MODE" (for model 204. 077/277/375)
No "kickdown" recognized (for transmission 722)

Function sequence for variable SPEEDTRONIC (without code (494) USA version)

The function variable SPEEDTRONIC limits the maximum speed of the vehicle variably from a speed of v = 30 km/h. For example, if the driver sets the limit of the maximum speed to v = 50 km/h then the maximum speed of the vehicle is limited to v = 50 km/h.

Acceleration or braking of the vehicle is controlled by the driver.

If the cruise control lever is switched to the variable SPEEDTRONIC, the cruise control is deactivated.

The variable SPEEDTRONIC is deactivated for:

Operation of the OFF switch

Kickdown (accelerator pedal pressed by & gt;90% and vehicle speed v <20 km/h away from selected maximum speed)

Function for vehicles without code (233) DISTRONIC PLUS and without code (237) Active Blind Spot Assist or without code (238) Active Lane Keeping Assist:

To do this a comparison is made as for the automatic speed control between the current actual speed with the target speed set by the driver by the electronic stability program control unit.

The electronic stability program control unit sends corresponding information to the CDI control unit or ME-SFI [ME] control unit which uses the values input by the electronic stability program control unit to calculate the corresponding dynamic vehicle parameters, while considering the driver's settings, for engine control. If the driver accelerates the vehicle to the limit of the target speed, the electronic stability program sends a request to reduce the engine torque to the CDI control unit or the ME-SFI [ME] control unit.

For vehicles with transmission 722, the A/T is downshifted is also necessary according to the operating condition to reduce the load on the service brake system.

Function for vehicles with code (233) DISTRONIC PLUS, code (237) Active Blind Spot Assist or code (238) Active Lane Keeping Assist: To do this a comparison is made as for the automatic speed control between the current actual speed with the target speed set by the driver by the video and radar sensor system control unit. The Electronic Stability Program control unit transmits the corresponding information via chassis CAN to the electronic stability program control unit.

The electronic stability program control unit sends corresponding information via the chassis CAN to the CDI control unit or ME-SFI [ME] control unit which uses the values input by the video and radar sensor system control unit to calculate the corresponding dynamic vehicle parameters in consideration of the driver's settings for engine control.

If the driver accelerates the vehicle to the limit of the target speed, the video and radar sensor system control unit sends a request to reduce the engine torque to the CDI control unit or the ME-SFI [ME] control unit. If the vehicle reaches the specified speed set by the driver in decel mode, for example by driving down a hill, then the service brake is actuated in a metered fashion over the traction system hydraulic unit by the ESP control unit.

To do this, the video and radar sensor system control unit sends a corresponding request, via the vehicle dynamics CAN, to the electronic stability program control unit.

For vehicles with transmission 722, the A/T is downshifted is also necessary according to the operating condition to reduce the load on the service brake system.

Additional function requirements for permanent limiter

Function of the permanent limiter is activated in the menu "Settings", the menu level "Vehicle" under "Limitation (winter tires)" in the IC.

The function of the permanent limiter can be activated independently of the status of the ESP.

Function sequence for permanent limiter

The maximum speed of the vehicle can be limited in v = 10 km/h or 5 mph steps of v = 160 to 240 km/h or v = 100 mph to 150 mph.

The set maximum speed is transmitted by the IC via the chassis CAN to the Electronic Stability Program control unit (without code (233) DISTRONIC PLUS and without code (237) Active Blind Spot Assist and without code (238) Active Lane Keeping Assist) or to the video and radar sensor system control unit (for code (233) DISTRONIC PLUS, code (237) Active Blind Spot Assist or code (238) Active Lane Keeping Assist).

Function for vehicles without code (233) DISTRONIC PLUS and without code (237) Active Blind Spot Assist or without code (238) Active Lane Keeping Assist:

If the vehicle reaches the maximum speed set by the driver, the electronic stability program control unit transmits a request to reduce the torque via chassis CAN to the CDI control unit or the ME-SFI [ME] control unit. If the vehicle reaches the maximum speed set by the driver in decel mode, for example by driving down a hill, then the service brake is actuated in a metered fashion over the traction system hydraulic unit by the ESP control unit.

For vehicles with transmission 722, the A/T is downshifted is also necessary according to the operating condition to reduce the load on the service brake system.

At about v = 10 km/h (v = 5 mph) below the set maximum speed a message is displayed in the multifunction display (A1p13) which indicates limitation of the maximum speed.

In the case of an active permanent limiter, the set speed cannot exceed the target speed set in the permanent limiter by the CC or variable SPEEDTRONIC (without code (494) USA version).

Function for vehicles with code (233) DISTRONIC PLUS, code (237) Active Blind Spot Assist or code (238) Active Lane Keeping Assist: If the vehicle reaches the maximum speed set by the driver, the video and radar sensor system control unit transmits a request to reduce the torque via chassis CAN to the electronic stability program control unit.

The Electronic Stability Program control unit passes on this request via the chassis CAN to the CDI control unit or the ME-SFI [ME] control unit which appropriately implements the request.

If the vehicle reaches the specified speed set by the driver in decel mode, for example by driving down a hill, then the service brake is actuated in a metered fashion over the traction system hydraulic unit by the ESP control unit. To do this, the video and radar sensor system control unit sends a corresponding request, via the vehicle dynamics CAN, to the electronic stability program control unit. For vehicles with transmission 722, the A/T is downshifted is also necessary according to the operating condition to reduce the load on the service brake system.

At about v = 10 km/h (v = 5 mph) below the set maximum speed a message is displayed in the multifunction display which indicates limitation of the maximum speed.

In the case of an active permanent limiter, the set speed cannot exceed the target speed set in the permanent limiter by the CC or variable SPEEDTRONIC (without code (494) USA version).

Electrical function schematic for cruise control (CC)	Without code (233) DISTRONIC PLUS Without code (237) Active Blind Spot Assist Without code (238) Active Lane Keeping Assist	PE30.30-P-2051-97FAA
	Model 204.0/2/3 with code (233) DISTRONIC PLUS with code (237) Active blind spot assist with code (238) Active lane keeping assist	PE30.30-P-2051-97FAB
Overview of system components for driver assistance systems		GF54.00-P-9998CE