started with a p0420 when i got the truck (straight piped) did the non fouler trick then cleared the codes. CEL came back this time for a p0138, discovered both o2 sensors were Bosch and were looking pretty old. so I replaced upstream and downstream with walker. from multiple forums I found the that Denso is a parent company to Walker so I figured they were a good option but after replacing both sensors and clearing codes again, the p0138 (stored) code came back along with a p0141 code (pending). When checking live data the upstream functions the way it should but the downstream stays at a steady 1v. I find it hard to believe the new o2 is the issue so to avoid replacing the DS o2 again i figured I would see if anyone has had this issue after replacing the sensor and how they fixed it. another thing to keep in mind my fuel gauge doesnt work (always empty, fuel light on) after replacing fuel pump twice. after some research i found that the ground wires of both sending unit and downstream use the same ground wires to the pcm. so im curious if these issues are related to the pcm being that the sensor ground wire seems to be the same pin location. I want to tackle this issue as fast as I can because I need to get registration in order. If this is the wrong forum to post in please tell me or transfer to the correct forum as needed. This is my first post on this forum so it's hard to tell where this belongs.

 

You are in the right spot. Welcome to DF.

If you still have the old O2 sensors, could try reinstalling the old one, and see what it does.

That said, just because it is "new", does NOT imply that it is "good".... Can't count the number of times I have gotten a bad part right out of the box.

 

well, since I didnt get the chance to use live data to see what the bosch sensor is doing I suppose i can give it a try. my only concern is that the other times I have seen a p0141 code pending or not only a couple of times it was actually the senor other times it was wiring. I haven't ran into a p0138 code before.

 

after checking the green wire which is the asd relay output I got absolutely zero voltage when turning key into on and with vehicle running and on the orange wire I have 1.5v in the on position. took apart the harness couldn’t see any problems with the wiring. Kinda stumped at what to do next.

 

Find splice 110. Should be on the left side of the engine harness somewhere. (left side when sitting in the drivers seat is my assumption.) See if you are getting power TO that splice.