I recently replaced the drivers side CAT and both upstream O2 sensors . The cat was cracked and rattling. The drivers side sensor 1 had a bad heater circuit (Po135), and the O2 sensor 1 on the passengers side would only read .07v constant. where the other three were reading .1 - .7volts.

I replaced both upstream O2 sensors with NGK sensors, and ran another scan today . bank 1 was fine .1 - .7 v (both) , but bank 2 sensor (one) upside was staying at .070 v and sensor 2 downside was .1 - .7 so I assume I have more problems. since the brand new sensor in bank2 sensor one is still reading .07 constant.

What do you think?

I'd test the wires for that sensor for continuity back to the ECM...my bet is that the sensing wire is grounded somehow.

is it possible a bad cat on that side could cause that low voltage reading?

Here's an update. I tested the o2 sensor wires from sensor to the PCM. Everything checked out fine. I also warmed the engine up and sprayed starting fluid all around looking for a vacuum leak. no luck there either