Use this article if…
- The MK4 does not mount a USB stick, drive, or accessory - not “phone projects but music skips.”
- Phone data for CarPlay/AA → Phone pairing. Unit won’t boot with USB inserted → Has power, won’t start.
Quick answer
When the MK4 ignores USB storage, rule out charge-only adapters and NTFS-only sticks first - try a small exFAT/FAT32 flash drive directly in the port with shallow folders, clean the socket, and avoid unpowered hubs.
Problem
- USB storage or a simple USB accessory is not detected by the MK4 when plugged into the factory USB port(s).
Symptoms
- No popup and no new source in the music/file browser.
- Port charges a phone but “unknown” or empty for storage.
- Worked until you added a hub or long extension.
- Only tiny drives work; large SSDs never appear.
Cause
- File system not supported (e.g. NTFS-only stick when the host expects FAT32/exFAT).
- Power-hungry SSD or unpowered hub browning out the port.
- Pocket lint or dash dust stopping data pins mating - power pins still touch.
- Cable or adapter is charge-only.
- Folder depth or file count beyond what the media scanner tolerates - looks like “empty.”
Fix Step-by-step
- Test a known small USB stick (≤32 GB) formatted exFAT or FAT32 with a few MP3s in the root folder - no hub.
- Blow out the port gently; re-plug with the vehicle in ACC and the MK4 awake.
- Remove USB‑C/Lightning phone cables - retry storage on its own.
- If you must use a hub, power it separately per manufacturer spec; MK4 ports are not meant for multi-drive farms.
- Recreate the library: shallow folders, Latin filenames, avoid DRM oddities for the first proof.
- After firmware or file copies from unknown PCs, scan the stick on a desktop for errors.
Notes
- Phone projection uses data-capable leads - see Phone pairing
- Random reboots with devices inserted: Resets or freezes
- Official updates: First boot / USB packages from PVS only