How to Troubleshoot Mercedes E320 / E350 Sound & Navigation

Troubleshooting video guide for 2002 to 2009 Mercedes E320 / E350 Sound & Navigation audio, navigation, display, and sound system

Common Problems

The unit starts up and shows the Mercedes-Benz display and then shuts down. This is usually caused by an open fiber-optic loop.

The radio intermittently loses audio for a few seconds. This could be a bad tele aid communication module.

Audio Compoents

Navigation unit.

Voice module.

Audio gateway.

CD changer.

Tele aid communication module.

Tools Needed
Screw drivers and/or torque set. Panel removal tools. Fiber-optic loop (lollipop).
Navigation Unit Removal Instructions (other components follow similar procedure)

In the trunk, remove the left quarter panel.

Remove the navigation unit screws on the bottom bracket.

Disconnect the plugs.

Insert the fiber-optic loop (lollipop) into the disconnected plug.

Turn on the ignition, and test to see of the issue has been resolved.

Useful Tips

We suggest checking the components first starting with the navigation unit, the CD changer, and then the voice module.

Only 10% of the time the command unit is bad. Usually, other components are the cause of issues.

The audio gateway cannot be tested using the fiber-optic loop (lollipop), so you may need to test this with another audio gateway unit. If FM/AM radio or the sound is distorted, it could be an audio gateway issue. Two 10 mm bolts on top and bottom must be removed (see video).

Voice module and tele aid communication modules are located under the carpet in the trunk. Remove the carpet, unscrew the bolts on each side to find the modules. Unplug the modules and perform the similar test above.

Remember to reconnect the modules after you try the other units.

Some units may require programming.

See our separate video for how to remove the command unit and CD changer.