Sony RMT-D254A Service Manual page 78

USB mode Error
Check
USJK1
(USB input jack)
Yes
Check UCON
(Pin #2,3,4)
Yes
Check MIC1
(Pin #V7,AB7,AB8)
Yes
Check VCC of MIC1 and peripheral parts
of Clock oscillation(12MHz UXAL)
No
Check between USJK1 and USCN1
No
Check between AVIC1 and 8YJK1
No
Check VCC of UIC1
6-15E