The problem is in the I/O bus (internal signal or power cables, system backplane, or I/O backplane). Use the following table to determine the part number for the field replaceable unit (FRU):
| CCIN or FFC | Type and model | Part number | Description | Location code |
| 2C8 | 9117-MMA | 42R7352 | I/O backplane | Un-P1 |
| 2C8 | 7311-D10 | 80P2339 | I/O (drawer) backplane | Un-P1 |
| 2C8 | 7311-D11 | 23R0181 | I/O (drawer) backplane | Un-P1 |
| 2C8 | 7311-D20 | 39J0515 | I/O (drawer) backplane | Un-P1 |