IBM 3270 Maintenance Manual page 241

Follow the steps below to run the diagnostic
routines.
1. Press 0 (RUN DIAGNOSTIC ROUTINES)
then press Enter.
(Skip Step 2 if you have only one display
adapter installed.)
2. Press Y or N (IS THE LIST CORRECT
(YIN)?)
then press Enter.
(If the list is not correct, follow the instructions
on your screen and correct the list before
answering yes.)
Press 0 (RUN TESTS ONE TIME) then press
Enter.
Press 7(MATH COPROCESSOR) then press
Enter.
The message on the screen below should appear
for ten seconds or less.
TESTING MATH COPROCESSOR
WAS THIS MESSAGE DISPLAYED FOR
TEN SECONDS OR LESS?
NO
Replace the Math Coprocessor and 8088
processor. See Section 5,
"Removal/Replacement and Adjustments"
YES
3-700-2 Maintenance Information