Use this article if…
- Your MK4 won’t mount a USB stick, drive or accessory, not “phone projects but music skips.”
- If it’s phone data for CarPlay or Android Auto, go to Phone pairing. If your unit won’t boot with a USB inserted, go to Has power, won’t start.
Quick answer
When your MK4 ignores USB storage you've plugged in, rule out charge-only adapters and NTFS-only sticks first. Try a small exFAT or FAT32 flash drive straight in the port with shallow folders, clean the socket, and skip unpowered hubs.
Problem
- Your MK4 doesn’t detect USB storage or a simple USB accessory when you plug it into the factory USB port(s).
Symptoms
- You get no popup, and no new source in the music or file browser.
- The port charges your phone, but storage shows as “unknown” or empty.
- It worked until you added a hub or a long extension.
- You only see tiny drives, and large SSDs never appear.
Cause
- You’re on an unsupported file system, for example an NTFS-only stick when the host expects FAT32 or exFAT.
- If you’ve plugged in a power-hungry SSD or an unpowered hub, it browns out the port.
- Pocket lint or dash dust is stopping the data pins mating, while the power pins still touch.
- Your cable or adapter is charge-only.
- Folder depth or file count is past what the media scanner handles, so you see an “empty” drive.
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, then re-plug with the vehicle in ACC and the MK4 awake.
- Remove USB-C and Lightning phone cables, then retry the storage on its own.
- If you must use a hub, power it separately to the manufacturer spec. MK4 ports aren’t meant for multi-drive farms.
- Recreate the library with shallow folders and Latin filenames, and skip DRM oddities for the first proof.
- If you’ve copied firmware or files from an unknown PC, scan the stick for errors on a desktop.
Notes
- You need data-capable leads for phone projection, see Phone pairing
- If it reboots at random when you’ve got devices plugged in: Resets or freezes
- Official updates: First boot / USB packages from PVS only