IBM 5155 Manual To Operations page 111

Test 900
Do you have an mM Printer Adapter installed in your
system?
NO - Continue with the next Test.
YES -
Did either of the following error messages
appear on your screen?
XX:XX:XX
ERROR - SYSTEM UNIT 9XX
XX:XX:XX
ERROR EXPANSION UNIT 9XX
YES -
Have the unit that contains the adapter
serviced.
NO - Your system has completed this test
successfully. Continue with the next Test.
January
1984 Test 900-1