Controlling The Cruise Control (Does Not Apply To Adaptive Cruise Control)
The following components are used when controlling the cruise control:
- Engine Control Module (ECM) (4/46)
- the steering wheel module (SWM) (3/130) (cruise control buttons), communicates with the central electronic module (CEM) (4/56) via LIN communication.
- the brake control module (BCM) (4/16) (brake pedal status, speed signal)
- Driver Information Module (DIM) (5/1) (cruise control light)
- transmission control module (TCM) (4/28) (cruise control active/not active, gear selector in "P"- or "N"- position)
- electronic throttle unit (6/120)
- stop lamp switch (3/9)
To activate cruise control the function must be switched on using the "CRUISE" button. A light is activated in the Driver Information Module (DIM). Cruise control is then in the so-called standby mode.
The driver activates the function by pressing the SET+ or SET- button. A message is then sent via LIN communication to the central electronic module (CEM), which sends the message on to the Engine Control Module (ECM) via the CAN network.
The Engine Control Module (ECM) controls the throttle angle so that a constant speed is maintained using the vehicle speed signal from the Brake Control Module (BCM). The transmission control module (TCM) also receives a message indicating that cruise control is active via the Controller area network (CAN), so that the transmission follows certain shifting patterns when the cruise control is active.
If the accelerator pedal (AP) is depressed the vehicle speed increases as normal and then resumes the stored value when the driver releases the accelerator pedal (AP) again.
The Engine Control Module (ECM) continually stores the speed selected with the steering wheel buttons. The stored speed is displayed in the Driver Information Module (DIM).
If the cruise control is switched off, for example, when the driver depresses the brake pedal, the system returns to standby mode. The stored speed is then displayed in the Driver Information Module (DIM) in brackets. The stored speed is resumed by pressing the "RESUME" button. The brackets around the selected speed disappear from the Driver Information Module (DIM).
The cruise control returns to standby mode if:
- the driver depresses the brake pedal
- the driver presses the "CRUISE" button on the steering wheel
- the driver presses the "0" button on the steering wheel
- the gear selector is in position "P" or "N
- if the speed deviates too much from the set value, for example, by the accelerator pedal (AP) being depressed for a longer time.
- certain diagnostic trouble codes (DTCs), which block continued activation, are stored. (For further information, see the appropriate diagnostic trouble code (DTC) information).