IBM 3270 Maintenance Manual page 263

1.
Set the Power Off on both the system unit
and expansion unit.
2. Remove the covers from both units.
3. Remove the asynchronous communications
adapter from expansion unit.
4. Remove the extender card. (This is the card in
the system unit that communicates with the
expansion unit.)
5. Plug the asynchronous communications
adapter into the vacant slot.
6. Go to 3-1100-1 to rerun the PIC then return
here and answer the question below.
DID THE DIAGNOSTIC COMPLETE
WITHOUT ERRORS?
NO
Replace the cable or adapter as instructed
by the screen message.
YES
3-1100-8 Maintenance Information