2000 S80 T6 FO2S Funny Reading

[syadd]

Hi all,

My first post here. I am suffering a strange problem which prevents me from passing emission inspection. Symptom: CEL is on, code is the common ECM-290A, front heated oxygen sensor bank 2 - Faulty signal.

The problem is, I replaced that sensor last week but the same code came back again. And when the engine is running, VIDA shows that both of the two front O2 sensors are giving constant 1volt reading, with occasionally flipping between 1 v and 1.00v, (which is the funny part). Back O2s are reading fine.

Now I am suspecting some kind of wiring issue. Any advice will be appreciated!