Cruise control (Tempomat) operation

The cruise control (Tempomat) GR 2 is operated by means of several operating elements:

Main switch

The main switch is designed as a push button.After switching the ignition lock to position 1 or 2, the cruise control (Tempomat) is set ready for operation by pressing the main switch.This standby mode prepares (arms) the system which must be carried out before switching on the cruise control (Tempomat). This function is intended to prevent the cruise control (Tempomat) being switched on by unintentional operation.

The Tempomat standby status is indicated by an LED in the instrument cluster.

After the system has been switched in standby mode and all switch-on conditions have been fulfilled, the cruise control (Tempomat) can be set into operation by pressing the "accelerate" button.

Tempomat standby mode is cancelled by pressing the main switch once again.Cruise control (Tempomat) operation is then not possible.The cruise control (Tempomat) standby can be cancelled at any time irrespective of the relevant vehicle status.The same applies when the ignition lock is switched in position 0 or when the cruise control (Tempomat) control unit detects a system defect.

Accelerate

The cruise control (Tempomat) is switched on by pressing the "accelerate" button on the steering wheel. When the button is pressed continuously, the speed is additionally increased with a comfortable acceleration progression.

The cruise control (Tempomat) is only switched on, however, when all switch-on conditions have been fulfilled.The switch-on conditions are:

• Tempomat prepared with main switch (if installed).
  
• Rest position of "accelerate" button before switching on the cruise control (Tempomat).
  
• Minimum speed of 30 km/h must be exceeded.
  
• The brake pedal must be in rest position.
  
• On vehicles with manual transmission, the clutch pedal must be in rest position.
  
• On vehicles with automatic transmission, drive stage "2" to "D" must be engaged.
  
• No switch-off conditions must be effective. Switch-off conditions are possible either by operating control elements (e.g. pressing the "OFF" button on the operating unit), or they can arise due to detected defect statuses (e.g. short-circuit at actuator motor).The defects are stored in the form of defect codes in the defect code memory.
  

After releasing the button, constant driving at the speed currently reached takes effect.

Decelerate

The speed is reduced from controlled cruise control (Tempomat) driving by pressing the "decelerate" button on the steering wheel.In this case, the deceleration capacity of the vehicle takes effect. The throttle is moved back from the current status to the idle position.This results in continuous speed reduction provided the braking torque of the engine and the terrain make this possible.

This procedure is effective for as long as the "decelerate" button is depressed.However, it is not possible to drop below the minimum speed.This makes it possible to specifically approach the minimum speed.

After releasing the button, constant driving at the speed currently reached takes effect.

The deceleration procedure can be interrupted by a switch-off condition arising:

• Switching off with the main switch
  
• Pressing the brake pedal
  
• Pressing the clutch pedal (manual transmission)
  
• Engaging the drive stages "P" or "N" (automatic)
  
• There must be no defect statuses (e.g. short-circuit at actuator motor).Defects are stored in the form of defect codes in the defect code memory.
  

Resume

Pressing the "resume" button makes it possible to switch on the cruise control (Tempomat) and to automatically approach a speed value already stored with specified acceleration progression and subsequent constant driving speed.A stored speed value can only be approached from uncontrolled driving by pressing the "resume" button.

Tip-up, tip-down

• Tip-up:
  The driving speed is increased in steps of 1 km/h by briefly hitting the "accelerate" button.
  The throttle must be outside the full load position.If this is not the case, button operation is ignored.
  
• Tip-down:
  The driving speed is decreased in steps of 1 km/h by briefly hitting the "decelerate" button.
  

Both functions are only implemented during controlled constant driving.The relevant button must not be pressed for longer than 0.5 s.If the button is pressed longer, the normal function "accelerate" or "decelerate" are carried out.

Comfort cutout

The cruise control is cut out smoothly by pressing the "OFF" button.

On reaching the idle position, however, after 2 s have elapsed at the latest, the positive lock between the throttle and control unit is cancelled by disconnecting the actuator clutch.The actuator remains in this condition until the next time the cruise control (Tempomat) is switched on.

Fast cutout

The quick cutout facility cancels the positive lock between the control unit and throttle by opening the actuator clutch.This procedure takes place within 0.5 s.

For safety reasons, the actuator motor is powered in throttle direction until the status "actuator clutch open" is detected.

This cutout condition is triggered by:

• Pressing the brake pedal
  
• Pressing the clutch pedal on vehicles with manual transmission
  
• Engaging the drive stages "N" or "P" on vehicles with automatic transmission
  
• Violation of a safety test:The control unit checks the inputs and outputs during cruise control (Tempomat) operation.The system is switched off if an implausible condition occurs at the inputs our outputs.
  

Transmission interface

A connection is provided between the transmission and Tempomat control units for automatic vehicles to ensure comfortable driving characteristics for controlled constant driving, acceleration and deceleration procedures.

The requirements of the Tempomat control unit necessitate a special transmission program for controlled driving.This transmission program ensures repeated gear change between adjacent gear stages is avoided.

The transmission program takes into consideration following driving statuses:

The information exchange between the Tempomat control unit and transmission control unit takes place via a single-wire link from the Tempomat control unit to the transmission control unit.Data transfer begins when the control unit supply voltage is applied.The Tempomat main switch has no influence on the start and end of data transfer.

If a data transfer fault occurs, for the transmission control this is equivalent to the status "cruise control passive".If, after a data transfer error, correct signals are received once again, they are once again taken into consideration by the transmission control.