Optimum Charging Controlled By Power Module (PM)
In order to drain as little energy as possible from the battery (particularly in the winter), the idling speed is increased at an early stage. This ensures that the battery charge level is kept high. If the charge level falls below the minimum required to be able to start the car, the idling speed is increased.
The PM detects that the battery charge level is low and places a message to that effect on the K-CAN P. The Car Access System (CAS) passes the message on to the K-CAN S. The ZGM receives the message from the CAS and passes it on via the PT CAN in its role of "gateway control unit".
The DME module receives the request to increase the engine speed over the PT-CAN. The DME passes that request on via the LoCAN to the Valvetronic control unit (VVT). The Valvetronic control unit controls the output stage for the valvetronic motors to increase the engine idle speed accordingly.