Lambda question 2.0 xev

[mr.c72]

Hi all, how are we all? Im having some issue's with a 2000 Vectra Sri 2.0ltr. Eml is on & is flagging up P0130 02 sensor low voltage on opcom.

Now when starting the car from cold with opcom using measuring blocks/live data, i can see the 02 sensor switch between open & closed loop, also the mv switches between 100 ish & 4500 ish. The mv will then stop registering on opcom after about 10 secs but will carry on switching between open & closed loop.
At idle there is a very slight missfire & i mean slight, can feel it through the car but cant hear a change in engine note.
I have tried what i thought was a working 02 sensor (used) but flagged the same fault, so im thinking its possibly not the 02 sensor thats at fault.
I did find a split pipe on the purge valve (now fixed) but has made no difference.
The engine otherwise is running sweet as a nut, little down on power but does not smoke. I dont want to go wasting £100 on a new 02 sensor if thats not the problem.

Any help appreciated guys.

[Vinci]

Other than a blocked cat I'm afraid the only option is a bad O2 sensor indeed... The first is fairly easy to spot by releasing a linkage towards the cat somewhere and see (apart from the increased noise) whether the fault goes away and maybe engine power being back up....

[mr.c72]

I cant release the linkage to cat, downpipe & cat all in 1 piece & cat is joined via a flexi, the only linkage is after the cat joining it to the center section & the car only had 1 lambda which is before the cat.
I think i will bite the bullet & replace the 02 sensor & go from there.