Mercedes-Benz W204 Start-Stop does not activate
Why does the W204's Start-Stop not activate?
The cause varies. The most common is a weak or faulty starter battery, in which case the ECO symbol stays lit and the engine does not stop. Also needed are, among other things, a fastened seat belt, good battery charge and suitable conditions. Short drives, long standing and cold can prevent the function.
How are the battery and the battery sensor related to Start-Stop?
Test the battery first; a weak battery charges poorly and the function is left out. A faulty battery sensor can prevent both Start-Stop and the HOLD function, and the car may report that it does not detect the driver. After the sensor was replaced, both worked.
Can the throttle body or the particulate filter prevent Start-Stop?
Yes. A sticking throttle body or too small a signal from its actuator caused fault codes and the ECO light not working. After the repair and the throttle body basic setting, the function returned. According to the service description, Start-Stop activates only when the particulate filter is in normal mode.