Cruise control (CC), function

The cruise control function belongs to the driver assistance systems and is integrated in the ESP and BAS control unit (N47-5). The cruise control also includes the following functions:

 Permanent Speed Limiter

 Variable Speed Limiter

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Variable and permanent speed limiters are also called Speedtronic control systems.

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Cruise control function requirements

 Circuit 61 ON (engine running)

 CC (cruise control) coded in the EIS control unit (N73)

 ESP not deactivated

 Vehicle speed > 30 km/h

 Parking brake not applied

 Selector lever in "D" position (with automatic transmission)

 CC push button (S40/4) in cruise control position
 LIM indicator lamp off

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Cruise control - general

The cruise control maintains the constant speed specified by the driver, irrespective of engine load condition and without the accelerator pedal being actuated.

Cruise control function sequence

The signals from the CC pushbutton are detected by the steering column tube module (N80) and transmitted to the ESP control unit over the engine compartment CAN (CAN C).

The ESP control unit sends the specified speed over the engine compartment CAN to the instrument cluster (A1).

The acceleration/deceleration requests (to engage the engine control) are sent by the ESP control unit over the engine compartment CAN to the CDI control unit (N3/9) or ME-SFI control unit (N3/10).

A request to automatic transmission for shifting gears is transmitted to the ETC [EGS] control unit (N15/3) or to the electric controller unit (VGS) (Y3/8) over the engine compartment CAN.

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To raise the speed (reach the specified speed), engine power is increased automatically and the automatic transmission is upshifted if necessary.

When the vehicle is approaching the specified speed, engine power is automatically reduced. If this is not enough to prevent the vehicle exceeding the specified speed for example, on a steep downward gradient), the service brake is applied and modulated and the automatic transmission downshifted as necessary.

If the vehicle is accelerated above the specified speed (for example, when overtaking), the cruise control reapplies the specified speed after the accelerator pedal is released.

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Activation

Pulling out the CC push button, or moving it up or down, activates the cruise control starting from a vehicle speed of 30 km/h.

If the CC push button is moved up or down, the current vehicle speed is stored as the specified speed and either raised or lowered depending on whether the pushbutton is moved up or down. If the CC push button is pulled out, the last specified speed stored is applied, provided a specified speed has been stored since the last engine start. If no specified speed has been stored, the cruise control sets the current vehicle speed as the specified speed.

The CC [TPM] switch can be moved up or down to increase or reduce the specified speed in 1 km/h or 10 km/h increments (two settings).

When the cruise control is activated, the specified speed setting is indicated on the multifunction display (A1p13) of the instrument cluster (A1).

Deactivation

The cruise control mode is deactivated by:

- Moving the CC push button switch to the "OFF" position

- Switching to Variable Speed Limiter
 LIM indicator lamp an

- Operating the service brake

- Operating the parking brake

- Selector lever in "N" or "R" position (with automatic transmission)

- ESP control intervention function

- deactivating ESP

- Vehicle speed <30 km/h

- Clutch pedal actuated for less than 6 s (with manual transmission)

- Circuit 61 OFF (engine off)