6. Abnormal plug and play operation
6.1 Abnormal DDC2
1) The host machine isn't communicating in DDC2 mode.
2) The video cable may have failed or may not to have connections for DDC.
3) Between I305 pin 6 and P302 pin 15 may have failed.
4) R337 open.
5) Cable failure.
Confirm the input of serial data on I305 pin 6 synchronize SCLK at TTL level.