No Sound - Common Navigation / Comand / Radio Problems
- Head Unit / Radio stuck on Mercedes-Benz logo
- Turns on and then off
- Shuts off randomly
- COMMAND will freeze
- Radio powers on but there is no sound
- Audio Gateway (AGW) drains the car battery
- Radio panel doesn’t turn on. (Hint: Check fuses.)
Most Common Solution
The fist thing you should try is to do a soft reset of the COMAND unit. To do a reset you will need to remove the fuses for at least 10 min for these systems:
- COMAND/ NAV / DVD Player / Radio
- CD Changer
- Voice Unit if equipped
- Audio Gateway AGW
By removing the fuses for these systems, you will be forcing the command unit to perform a rest. This will generally fix the problem. There is a chance that the symptoms may return again. If after a few weeks you are having the same problem, check with your Mercedes-Benz dealer to see if they have any updates for your comand / navigation unit.
How to do a soft reset of the COMAND / NAV Radio System
Here are the instruction on how to reset the audio/radio/command/cd changer system on a E-Class W211. If you have different Mercedes-Benz model, you will have different fuse numbers assigned to your command, radio, CD changer and audio gateway. Look up the fuse chart for your model to identify the fuses for these components.
Locate the fuse box on the side of the dash on driver’s side.
Remove the fuse box cover.
Locate fuse 26 and 28. Remove both fuses.
Locate the fuse box on the rear. Start by opening the trunk. The fuse box is located on the left side of the trunk.
Remove fuse #6
The fuse number will be different depending on the model of Mercedes-Benz that you have. The fuse numbers provided here apply to E-Class W211 2003-2008
Remove the key from the ignition and let the car stay off for at least 15 min.
Troubleshoot fiber optics.
If removing the fuses does not solve your problem, the next step would be to troubleshoot the fiber-optic loop. Mercedes-Benz uses fiber optic cables to transmit the sound signal between the different units. Fiber optics provides a faster transfer rates and better sound quality. All the audio related systems in the car are connected via the fiber optic cable in series, forming a ring or a loop. The signal will travel through all the different components and return back to the same component if required.
Components that are part of the fiber optic ring are:
- Head Unit / Comand / Navigation / DVD / Radio Head unit Audio 50 APS
- CD Changer
- Communication platform
- Voice recognition module
- Audio Gateway (can not bypass)
When one of these components (in yellow) goes down your COMAND will stop functioning. Let’s say your CD changer fails. You will not be able use the COMAND at all. The system will turn on and then off or will turn on but you will have no sound.
The COMAND will typically power on and then go off, get stuck, have no sound or not power on. If this happens do not automatically assume that the issue is the head unit.
To solve this problem you need to figure out which component is defective. You can do this by bypassing the different components until you find the probem. You will need a Fiber Optic Loop Adapter to bypass the system, one at a time until your COMAND system will work.
If you bypass a component and the problem is not solved, then try the next component on the list. The Audio Gateway AGW can also be defective. That is the brains of the Mercedes-Benz COMAND system, therefore you can not bypass it. You will need to replace the whole unit. The only testing that you can really perform with the AGW, is to make sure it is getting power. Unless if you have a STAR Diagnostic C4 or C3 you will not be able to troubleshoot the AGW any further.