IBM 3270 Maintenance Manual page 311

8. Set the Power switches for all work station
devices to On.
9. Rerun the fixed disk diagnostics, (see page
3-1700-1) then return to this page and answer
the question below.
DID THE TEST FINISH WITHOUT AN
ERROR?
NO Replace the fixed disk drive adapter. See
Section 5, "Removal/Replacement and
Adjustments"
YES
3-1700-24 Maintenance Information