MEX-N4000BE, MEX-N4000BT, MEX-N4050BT, MEX-N4070BT - Sony Car Audio Service Manual (repair manual). Page 12

AFFIXING  OF  LABEL (SERIAL  NUMBER)
When the front panel (SV) (assy) is replaced, it is necessary to af-
fi x the label (serial number).
2 labels (serial number) are included with a new front panel (SV) 
(assy). Affi x 1 label to the rear side of the front panel (SV) (assy). 
Affi x the other one to the bottom side of main unit.
Be sure to perform this procedure, as Bluetooth will not operate 
correctly if the serial number of the front panel (SV) (assy) and 
main unit do not match.
Also, since the serial number has changed, print page 13 and hand 
the tear-off with the product to the customer when returning the 
product after repairs are complete.

5.  The Factor that One Touch Connection is Impossible 
The four following factors are considered as the factor that one touch connection is impossible. 
Guess and check the defective factor by each checking result.

Note: The four following factors are examples.

1 BT module defect

NG

―

NG

NG

2

Knob (VOL) (SV) 
assy defect

OK

NG

OK

NG

3

NFC tag data 
writing failure

OK

NG

OK

NG

4 Smartphone

OK

OK

OK

NG

Check the version of the NFC tag data writing application 
(NFCtagWriter application) for the servicing according to the 
procedure below.

Procedure:
1.  Start the NFCtagWriter application on the smartphone.
2.  Tap the “ 

 ” (menu button) or “   ” of the screen of the smart-

phone, then tap the “About” that is displayed on the screen of 
the smartphone.

3.  Check that version of the NFC tag data writing application for 

the servicing is displayed on the screen of the smartphone.