Teaching the operating values of the SMG gearbox

On vehicles with SMG gearboxes specific operating values of the gearshifting are stored in the gearbox controls GS30 / GS35. Teaching and saving or resetting these values can be run via the service functions.

Service functions

• Teach gearbox
  This service function comprises three steps:
  - Teaching the H shift pattern - Teaching the clutch slipping point - Resetting the clutch characteristics
  
• Recalibrate gearbox
  This service function enables renewed calibration of the H shift pattern after long a service period of the vehicle.
  
• Reset clutch characteristics
  This service function enables a reset of the learned clutch characteristics.
  

Teaching steps

The individual steps involve the following actions:

• Teach H shift pattern
  For smooth gearshifts, the values of the selection path sensor and of the selector angle sensor of the individual gears must be stored in the control unit. To do so, a service function automatically engages the individual gears and stores the sensor values. Sustained storage of the values is ensured on switching off the ignition for 15 seconds after running the function.
  
• Teach clutch slipping point
  The contact point of the clutch (clutch slipping point) is determines with the engine running. Here, the vehicle must be secured against moving off. To determine the clutch slipping point, the clutch is opened automatically using the service function and closed again slowly. When the control unit registers the first transfer of torque, the current value of the clutch sensor is stored as the contact point. Sustained storage of the values is ensured on switching off the ignition for 15 seconds after running the function.
  
• Reset clutch characteristics
  The clutch characteristics include the features if the linings and behaviour of the clutch spring (plate spring hysteresis). Resetting the characteristic values enables renewed teaching to start. Teaching takes place automatically from the control unit during the first movements of the vehicle. NB: This adaptation process is only concluded after driving off a number of times, preferably with the engine cold.