What should I do if a USB device is not recognized or shows a 'Check USB' error?

The CHECK USB error means the USB connector or USB cable has short-circuited, or the connected USB device is drawing more than the maximum allowable current. Disconnect the USB device, turn the ignition switch OFF and back to ACC or ON, and reconnect only a compliant USB device. Also note that connections via USB hubs are not supported — the USB device must be connected directly to the unit using a USB cable. (Page 41, 45)