IBM pSeries 670 Service Manual page 336

b. If the hang repeats, check with service support to see if there is a firmware update that fixes the
problem.
c. If there is not, or the update does not fix the problem, replace the following FRUs, one at a time, in
the following order:
1) Modem cable
2) Modem
d. If this procedure does not fix the problem, call service support.
316 Eserver pSeries 670 Service Guide