98 I30 DTC P0138-139

[melsauto]

98 Infiniti i30 federal 3.0 checked and found codes P0138-P0139 codes.Hooked up scan tool and checked found bank 1 sensor two after cat always stays at 0.30 no matter what.Also how many sensors does this vehicle have. I could only see 3 sensorsone on each bank below the exhaust manifold., and one after the cat. The confusing thing is the failure code 138 and 139 are for bank 1 sensor 2 voltage high. I only see one oxygen sensor after the cat. I replaced the sensor after the cat with a universal bosch sensor still the reading stays at 0.30 does not switch.Any and all info will be appreciated.