P0157 Chevrolet - code wont go away

Question

2004 CHEVROLET SILVERADO 5.3L "T"
switched sensors from side to side still the P0157
watch sensor work when in open loop, but when it goes
into closed loop 3 sensor seem to work proper
just that one sensor B2S2 works its way down
and just stays way low not moving up & down
has new at on just bank 2