I know you fan find replacement optical pick ups on ebay for ther BMW drives, not sure if they have them for the NAV disc in the E70.

They are usually around $40 or so and not so hard to replace if you have the skills to do that kind of work. Most of these pick ups have a solder ball that needs to be removed that is like anti static protection for the pickup. I also suspect you can find places on line that repair/replace the pickups as well if you cannot find parts or do not want to tackle the project.

Sometimes burned discs are harder to read than original disc. You might try to copy and reburn a new disc or just purchased some update map disc on ebay and see what happens.

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2008 4.8i Black with Tabacco. Black Y-spoke wheels and shadowline trim.