Fixing error code 137/177

[VTRangeuh]

Check engine light came on with stored codes 177 and 542. Tested running and got 177 I'm gonna replace the whole fuel sender assembly, but I'm not quite sure where the o2 sensor is to be replaced. I was under the impression there were 3 (based on a YouTube video) but I can't find the one downstream of the cat.

I have a 1993 3.0 standard cab short bed. Where is the 137/177 O2 sensor located and what's the easiest way to get er out.

Thanks

 

[VTRangeuh]

Its the one on the driver's side. I unplugged it and the code went fron 137 to 136. Replaced it ran it and the 137 code was back so not sure if I got a bad part or what. I ran the cylinder balance test before and it was all clear. However I ran it after replacing and now its saying cylinder 5 is bad. I'm gonna replace the injector in a bit once it cools some and I'll see if that finally resolves the code.