2008 GL450 4MATIC's Navigation is not funtional.

**Answering for completion**

When it comes to the newer COMAND Mercedes radio, they use a automotive HDD, not a map DVD - that was a thing on 90-erarly 00’s cars when hard drives were expensive, but DVDs were cheap. After the COMAND system came out, they went to loading the maps onto the hard drive and only use the DVD for updates.

If the navigation isn’t working, either the maps on are corrupted (you may need to “restore” it with a previous map DVD then use the 2015 DVD, or "reflash" it at the dealer/get a used HD with maps to work with), unless the HD failed. IF the drive is dead, you may need a used drive from a failed radio, or a replacement radio from a wrecked car if the drives are paired and update it. You need the following update DVD: A169 827 92 59 - BQ 6 46 0328 - Version 12.0.
If the issue persists, the laser on the radio may be dirty/dead (these aren't like the old cars like the W140 S600 from Japan which used DVDs, as well as early US cars). The quickest way to rule out a lens issue is to use a cheap/burned CD and see if it plays reliably; if it plays fine, the laser is having trouble with DVDs but not CDs and is partially defective.

NOTE: check the center console and glovebox first, otherwise it’s in the trunk. Some models did that but copied the map files to the HD for quite a few years. Even if you can update it, the final updates for yours are 7+ years old! If anyone is seeing this and still wants to try it feel free, but the best option with a failed drive and lost maps will be to get a “formatted” drive and update, or a parts COMAND radio with good maps (update if desired), or a LMT Garmin if you do not use your phone.

This is what the DVD looks like: