Distributed function: Notes

The Digital Engine Electronics is the master control unit for the automatic start-stop function. It reads in all the input signals and the switch-off inhibitors and switch-on prompts communicated by other systems. Based on this information, the DME decides when the combustion engine is to be switched off and restarted.

Basically the combustion engine is switched off when in drive (position "D") the vehicle speed reaches 0 mph and the car is held at a standstill. The vehicle speed is determined with the aid of the wheel speed sensors, the Dynamic Stability Control and the Integrated Chassis Management. Holding at a standstill is detected by reference to the brake light switch signal or to the status of the Automatic Hold function. Starting of the combustion engine always occurs automatically when the driver outputs the "not actuated" brake light switch signal or the accelerator pedal angle is greater than 0° (especially if the Automatic Hold function was previously activated).

In addition to these generally applicable conditions there are several other situations which limit the automatic start-stop function. These conditions are listed in the following chapters.

Several logically related conditions are summarized into groups in the following table. In the event of a customer complaint, an exact analysis of the system can be done using the ISTA diagnostic system.