DU4 red x.  Left AND right reversionary work. EIED left and right work. Left reversionary works.

3270 – 81 is “DU4 is not receiving the EFIS Graphics Bus Data”

3270 – 90 is “No reversion modes were active”

so the EDS Fault summary sees the problem  as IAC2-DU4 interface  problem.

 

Figure 8-14 shows ASCB , which is 3-254, near page 259

ASCB elead wire pulled free from pin 38.