Low Voltage On O2 Sensor

[pwey84]

i have a PO300 code on my tahoe 2000 5.3 vortec with 80KMiles on it,

 

on the memoscan the O2 voltage are at idle:

 

O2S11 : 0,1 to 0,6V

O2S12 : 0,815V

O2S21 : 0,1 to 0,8V

O2S22 : 0,05 to 0,065V

 

The O2S22 seem to be low?

 

the O2 sensor were never replaced.

 

i have checked different things before, replace plug and wire, verify EGR, cleaning throtle body....

 

any Idee?