Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Radio Systems
Radio Systems
- "Chorus"
- "Concert"
- "Symphony"
Speaker Systems
- Active speakers (rear speakers use Amplifier/Woofer (in left rear luggage compartment) -R44-).
- BOSE sound
Radio Preparation
4 or 6 passive speakers and rear window antennas.
General Information
From KW 22/04, the "chorus" has a second antenna connection (IF).
Radio generation II+ introduced from KW 45/06.
This uses two internal tuners with "phase diversity" for reception.
Further removal steps are the same as with the "symphony" radio.
Besides switching diversity, "phase diversity" is the second procedure for reducing reception interference.
At least two antennas with an amplifier and a radio -R- with two tuners are required.
If the signal received is interrupted, both signals are digitalized and separated in the tuners in the radio so that the disrupted signals are blocked out as much as possible.
If the reception signal is not disrupted, the radio constantly compares which antenna has the strongest reception. This is then transferred.
In this case, the second tuner checks the frequency band in the background for better reception frequencies for the selected station. If a better signal is found, this tuner switches to reception and the other to the background.
Communication with other vehicle systems takes place via the Infotainment CAN-Bus and Data Bus On Board Diagnostic Interface -J533-.
Fault finding is performed via "Guided Fault Finding" using the Vehicle Diagnosis, Testing & Information SystemVAS5051.
Repairs on antenna wires, refer to ANTENNA WIRES, REPAIRING .
Repair to CAN bus lines, refer to CAN BUS WIRE, REPAIRING .
Transport Mode in "Symphony II+"
The "symphony" generation II+ has a special protection lock for the internal CD changer.
This is active when the unit is shifted and must be deactivated after installation.
In the same way, the transport protection must be activated before removing the unit.
Transportation mode, activating and deactivating, refer to RADIO, SYMPHONY II+ IN TRANSPORT MODE, ACTIVATING/DEACTIVATING .
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.