Help With These O2 Readings

[walt]

Background - this is my daughters 2001 Nissan Sentra GXE that she drove with a missfire due to a faulty ECM. I replaced the ECM and now the check engine light is on. I originally thought she fried one or both of the catalytic converters. The fault code is P0420 catalyst efficiency bank 1 but, aren't these good readings for
B1?


B1 S1 .13 to .72 VDC
STFT B1 S1 -2.3 to - 5.4%

B1 S2 .13 to .14 VDC
STFT B1 S2 99.2% (cycles between rich and lean but mostly lean)

B2 S1 .11 to .61 VDC
STFT B2 S1 -.7 to -3.1% (reads lean)

B2 S2 .12 to .16 VDC
STFT B2 S2 99.2% (cycles from rich to lean)

Can anyone advise on the condition of the O2 sensors and catalytic converters given the above info? The car has two converters and I assume the first is a precat or bank 1. Thanks for the help.

Walt
911SC