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

MODEL 453.0 (except 453.091), 453.3 (except 453.391), 453.4 (except 453.491) 

with CODE 440 (Cruise control) 

G12094820Courtesy of MERCEDES-BENZ USA

Function requirements, general 

Cruise control/variable speed limiter, general points 

The CC (TPM) function is subdivided into two main functions:

Cruise control, function 

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. The function CC is implemented in the ME-SFI [ME] control unit. Evaluation of the variables and implementation of the CC function occurs by the ME-SFI [ME] control unit.

The cruise control function is subdivided into the following subfunctions:

Operation and display of the CC 

Cruise control/variable speed limiter switch group on MFL 

G12094821Courtesy of MERCEDES-BENZ USA

Display on the CC shown on vehicle with code K35 (IC with a monochrome display) 

G12094822Courtesy of MERCEDES-BENZ USA

The CC is switched on by pressing the CC/variable speed limiter switch upwards. The CC symbol (1) is displayed in the multifunction display.

The desired speed is adjusted and stored over the accelerate and set switch. Using the "Resume from memory" switch the last stored or the current vehicle speed is set as the target speed. Using the accelerate and set switch and the decelerate and set switch the target speed can be altered. To do this press either the accelerate and set switch or the decelerate and set switch until the desired speed is reached; the speed is increased or decreased in steps of v = 1 km/h. Or hold down the accelerate and set switch or the decelerate and set switch until the desired speed is reached. The set target speed is displayed over the CC target speed display (2) in the multifunction display of the IC (except for code 494 (USA version)). For vehicles with code 494 (USA version) the note CC "SET" (2.1) for the activated CCs is displayed instead of the set speed. Using the switch off switch the CC can be temporarily deactivated. The cruise control is re-activated using the resume from memory switch. The CC is switched off again by switching the CC/variable speed limiter switch into the center position or by switching on the variable speed limiter function. The CC symbol (1) goes out.

IMPORTANT Detailed information about information flow can be obtained from the Chapter "Evaluation of the input factors". Detailed information about operation can be taken from the operator's manual.

If the CC function is impaired, the CC error symbol (3) appears (CC symbol flashes) for t ≈ 10 s and then goes out again. For vehicles with code K36 (IC with a colored 8.9 cm (3.5") display) the fault message "CC nonfunctional" is also displayed in the multifunction display. The CC function is then deactivated automatically. To do this the ME-SFI [ME] control unit transmits the status of the CC with the respective request to activate the CC error symbol (3) via the interior CAN to the IC.

Evaluation of input factors 

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

Operating condition of engine running (function requirements)

The ME-SFI [ME] control unit recognizes the operating condition "engine running" based on the engine rpm (computed) from the crankshaft position sensor (L5). To do this it also transmits the engine rpm via the interior CAN (CAN B) to other control units.

Parking brake status:

The IC reads in the status of the parking brake over the parking brake indicator switch. To do this the IC reads in the signal from the parking brake indicator switch via a direct line. If the parking brake is actuated, the CC cannot be activated. Also the speed control of the CC is interrupted if the parking brake is actuated.

Accelerator pedal position:

The ME-SFI [ME] control unit recognizes the accelerator pedal position and the kickdown position from the direct signals from the accelerator pedal sensor and evaluates these. For kickdown the vehicle can be accelerated beyond the target speed despite a set CC. After the acceleration process the CC regulates the vehicle again to the set target speed.

Engaged gear stage (function requirements for vehicles with code 429 (twinamic))

For vehicles with a DKG (code 429 (twinamic)) the status of the engaged gear stage is transmitted by the DKG control unit via the drive train CAN (CAN C) to the ME-SFI [ME] control unit. The CC can only be activated again for an engaged gear stage of the DKG.

If a control intervention function occurs by the ESP®, the Electronic Stability Program control unit sends the information "ESP® control" to the ME-SFI [ME] control unit which responds by deactivating the CC function.

Autonomous brake application (vehicles with code 258 (Active brake assist)):

If the driver does not react to a collision-critical warning by the Brake Assist (proximity warning function with active brake application), the control unit proximity warning function with active brake application initiates autonomous braking and the reduction of engine torque via the control unit electronic stability program. The control unit proximity warning function with active brake application sends the status active brake assist (system status) of a stationary object or object in front, the relative speed in m/s as well as the distance to the stationary object or the object in front in diverse CAN messages via the front end CAN to the center SAM control unit. The center SAM control unit then sends these CAN messages via the interior CAN to the electronic stability program in order to initiate the braking torque. The Electronic Stability Program control unit evaluates the incoming requests, actuates the traction system hydraulic unit directly, and sends the request to reduce engine torque via the interior CAN to the ME-SFI [ME] control unit.

Deactivation in the case of a crash:

In the case of a crash the Supplemental Restraint System control unit transmits the crash signal to the ME-SFI [ME] control unit which responds by deactivating the CC.

Automatic speed control by the CC 

Additional function requirements for automatic CC speed control:

Function sequence for automatic CC 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 target speed is displayed over the CC target speed display (2) in the multifunction display of the IC. To do this the ME-SFI [ME] control unit transmits corresponding requests via the interior CAN to the instrument cluster.

The following activities are started or initial parameters (requests) issued in order to reach or maintain the target speed:

Raise/reduce engine torque:

The ME-SFI [ME] control unit evaluates the input factors as well as further driving dynamics requests and raises or reduces the engine torque as required in order to maintain the vehicle at the target speed set by the driver. The IC sends the set target speed redundantly to the speed stored in the ME-SFI [ME] control unit, via the interior CAN to the ME-SFI [ME] control unit.

Adaptive switching control (vehicles with code 429 (twinamic)):

For vehicles with a DKG (code 429 (twinamic)) the ME-SFI [ME] control unit transmits the status of the CC (CC active or variable speed limiter active) with the accelerator pedal status (actuated or unactuated) via the drive train CAN to the DKG control unit. According to status the DKG control unit reacts adaptively to the status and therefore the request of the CC system. Downshift or upshift of the A/T takes place autonomously through the DKG control unit itself, dependent on the current operating condition.

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

Reverse gear not engaged

For vehicles with code 410 (5-speed manual transmission) an engaged reverse gear is recognized based on the signal from the reversing light activation/idle recognition switch. The center SAM control unit reads in the reversing light activation/idle recognition switch over a direct line and transmits the "reverse gear engaged" signal via the interior CAN to the ME-SFI [ME] control unit. For vehicles with a DKG (code 429 (twinamic)) the engaged gear stage is sent via the drive train CAN to the ME-SFI [ME] control unit. The CC cannot be activated for an engaged reverse gear.

Transmission not in neutral (function requirements)

For vehicles with code 410 (5-speed manual transmission) neutral is recognized based on the signal from the reversing light activation/idle recognition switch. The center SAM control unit reads in the reversing light activation/idle recognition switch over a direct line and transmits the "transmission in neutral" signal via the interior CAN to the ME-SFI [ME] control unit. The ME-SFI [ME] control unit reacts by interrupting the CC function.

Vehicle speed (function requirements)

The vehicle speed is calculated from the wheel speed from the front axle rpm sensors and the rear axle rpm sensors. The Electronic Stability Program control unit transmits the respective information about the vehicle speed via the interior CAN to the ME-SFI [ME] control unit. Switch position and driver request over the CC/variable speed limiter switch group (function requirements):

The ME-SFI [ME] control unit reads in the driver requests over the CC/variable speed limiter switch group over direct lines from the steering wheel clock spring contact. The ME-SFI [ME] control unit recognizes the respective driver request over the respective different signal voltage which is applied for the different switch positions.

Clutch pedal position (vehicles with code 410 (5-speed manual transmission)):

For vehicles with a manual transmission the position of the clutch pedal is read in over the signals from the clutch pedal switch. To do this differentiation is made between clutch pedal depressed and clutch pedal unactuated. The center SAM control unit reads in the positions of the clutch pedal switch over direct lines and transmits the pedal position via an interior CAN to the ME-SFI [ME] control unit. The ME-SFI [ME] control unit deactivates the CC function when the clutch pedal is depressed. The CC can also only be activated if the clutch pedal is not actuated.

Brake pedal position:

The position of the brake pedal is read in over the signal from the brake lights switch. The center SAM control unit reads in the positions of the brake lights switch over a direct line and transmits the pedal position via the interior CAN to the ME-SFI [ME] control unit. The ME-SFI [ME] control unit deactivates the CC function when the brake pedal is depressed.

Throttle valve position

The ME-SFI [ME] control unit evaluates the signals of the throttle valve actuator for feedback of the throttle valve position. The CC cannot be activated for an implausible signal from the throttle valve actuator.

Control intervention function of the Electronic Stability Program (ESP®)

IMPORTANT Detailed information about the information flow of the events which lead to deactivation of the automatic speed control can be taken from the chapter "Evaluation of input factors".

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).

Variable speed limiter function (only vehicles without code 494 (USA version)) 

Additional function requirements on the variable speed limiter:

The permissible 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 speed limiter function. The driver can accelerate the vehicle up to the set limit. The permissible maximum speed set by the driver is displayed by the display in the multifunction display of the IC.

The variable speed limiter function is subdivided into the following subfunctions:

Display on the variable speed limiter shown on vehicle with code K35 (IC with a monochrome display) 

G12094823Courtesy of MERCEDES-BENZ USA

Operation and display of the variable speed limiter 

The variable speed limiter is switched on by pressing the CC/variable speed limiter switch downwards. The variable speed limiter symbol (4) is displayed in the multifunction display. The desired permissible maximum speed is adjusted and stored over the accelerate and set switch. The permissible maximum speed set by the driver is displayed by the permissible maximum speed variable speed limiter (5) display in the multifunction display of the IC. The last stored permissible maximum speed is set by the "Resume from memory" switch. The set permissible maximum speed can be altered over the decelerate and set switch and the accelerate and set switch. To do this press either the accelerate and set switch or the decelerate and set switch until the desired permissible maximum speed is reached; the permissible maximum speed is increased or decreased in steps of v = 1 km/h. Or hold down the accelerate and set switch or the decelerate and set switch until the desired permissible maximum speed is reached. The desired permissible maximum speed is then increased or decreased in steps of v = 10 km/h. The set permissible maximum speed is displayed by the permissible maximum speed variable speed limiter (5) display in the multifunction display of the IC.

Exceeding the permissible maximum speed set by the driver for kickdown: 

If the driver presses fully down on the accelerator pedal and the ME-SFI [ME] control unit recognizes the kickdown position, the variable speed limiter is deactivated temporarily and the vehicle can be accelerated beyond the permissible maximum speed set by the driver. In the multifunction display the warning variable speed limiter exceeding the maximum speed (6) (flashing display of the variable speed limiter permissible maximum speed) is displayed for the period in which the speed is exceeded. The variable speed limiter is activated again automatically as soon as the vehicle speed goes down below the permissible maximum speed set by the driver.

IMPORTANT Detailed information about information flow can be obtained from the Chapter "CC function" in the subfunction "Evaluation of input factors".

Deactivation and switching off of the variable speed limiter: 

Using the switch off switch the variable speed limiter can be temporarily deactivated. The variable speed limiter is re-activated with the last stored permissible maximum speed using the resume from memory switch.

The variable speed limiter is deactivated again (switched off) by switching the CC/variable speed limiter switch into the center position or by switching on the CC function. The variable speed limiter symbol (4) goes out.

If the variable speed limiter function is impaired, the variable speed limiter error symbol (7) appears (variable speed limiter symbol flashes) for t ≈ 10 s and then goes out again. For vehicles with code K36 (IC with a colored 8.9 cm (3.5") display) the fault message "Variable speed limiter nonfunctional" is also displayed in the multifunction display. This variable speed limiter function is deactivated automatically. To do this the ME-SFI [ME] control unit transmits the status of the variable speed limiter with the respective request the variable speed limiter error symbol (7) and the warning message to activate via the interior CAN to the IC.

IMPORTANT Detailed information about operation can be taken from the operator's manual.

Automatic speed limiter by the variable speed limiter 

If the set limit was reached, the following activities are started:

The ME-SFI [ME] control unit evaluates the input factors as well as further driving dynamics requests and raises or reduces the engine torque as required in order to maintain the vehicle at the set permissible maximum speed set by the driver. The IC sends the set permissible maximum speed redundantly to the speed stored in the ME-SFI [ME] control unit, via the interior CAN to the ME-SFI [ME] control unit.

Adaptive switching control (vehicles with code 429 (twinamic)):

The ME-SFI [ME] control unit transmits the status "Variable speed limiter active" with the accelerator pedal status (actuated or unactuated) via the drive train CAN to the DKG control unit. According to the situation the DKG control unit reacts adaptively to the status "Variable speed limiter active" and downshifts the gear stage. Downshift or upshift of the A/T takes place autonomously through the DKG control unit itself, dependent on the current operating condition.

Optical and acoustic warning 

If the vehicle exceeds the permissible maximum speed set by the driver and if the activities "Reduce engine torque" and "Adaptive switching control" are not sufficient to decelerate the vehicle down to the permissible maximum speed set by the driver, the driver is made aware of the fact over the warning variable speed limiter exceeding the maximum speed (6) (flashing display in the variable speed limiter permissible maximum speed) that he must reduce the speed by braking or downshifting. A warning tone is also output over the warning buzzer in the IC. To do this the ME-SFI [ME] control unit transmits corresponding requests via the interior CAN to the instrument cluster.

  Electrical function schematic for cruise control (CC)   PE30.30-P-2051-97BBA 
  Overview of system components for driver assistance systems   GF54.00-P-9998KJ
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