IBM 6151 Maintenance And Service Manual page 301

Step 9
The diagnostics can be run in loop mode by selecting the Run Test
Multiple Times option in the TEST METHOD SELECTION menu.
Run the diagnostics in loop mode for several minutes on each
device you think is failing.
DID THE DIAGNOSTICS FIND A PROBLEM?
YES Do the following steps:
1. Record the name of the FRU for each SRA in the SRN.
The FRUs are listed in the most likely to fail order.
2. Exchange each FRU one at a time. Check each FRU by
running the diagnostics in loop mode for several
minutes.
NO No trouble was found. If you still have a problem, contact
your service support person.
(6/88) Problem Isolation Charts 3-0090-9