What does the 'CHECK USB' error message mean and how do I fix it?
The CHECK USB error means the USB connector or 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 only reconnect compliant USB devices. Also check that the USB connector or cable is not caught in something or damaged. (Page 41)
From the official Pioneer DEH-S7200BHS Car Receiver manual, page 41
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