Lack of audio or cell phone functionality may be related to the failure of the audio gateway module.
Resources for the Repair and Maintenance of your 2009 Mercedes-Benz E320 BLUETEC
2009 Mercedes-Benz E320 BLUETEC
2009 Mercedes-Benz E320 BLUETEC Problems
High mileage or older vehicles commonly develop leaks from the differential seals and/or cover. Our technicians recommend a complete reseal of the differential unit whenever these leaks are repaired.
The early versions of the central gateway module (which allows different systems to communicate with each other) have software problems.
Water can damage the weight sensor in the front, passenger seat, causing the SRS (airbag) light to illuminate. There is an electrical component in the seat cushion susceptible to fluid damage. Any spills should be dried up immediately in order to try and prevent damage to the sensor.
It is not uncommon to encounter premature failure of the anti-lock brake system (ABS) modulator assembly due to dirty brake fluid. Our technicians recommend flushing the brake fluid every two years in order to help prevent this problem.