can anyone tell why o2 sensors quit working?

I have a new build and I am working on getting the o2 sensors to work right. I have fueling real close with the wideband, but I have the o2 sensors in there so it would be nice to have them doing something. I figured at first that the o2 sensors might have been bad, so I replaced them with some from another vehicle I have which I know were good. They are working for a while until the coolant temp got up to like 120 degrees. I have stft just enabled in open loop. At the 6:10 mark stft stopped working and just a little later the o2 voltage goes to .447. Anyone have any suggestions? thanks

Go to Oxygen Sensors>Closed Loop Enable and put that table back to stock values.

I had it like that also and it doesn't make any difference. I put them to 120 degrees. I have a log of it and they work for just a little bit then they stop. First log is when they stop working, then I logged it again when the coolant temp was a little higher. Still aren't working.

I'd be checking the harness for problems and the fuse block to make sure it's all good.

I could, it is a brand new harness. But I guess that doesn't mean much. I got the cheapest harness off of amazon and found multiple issues with it, so then I bought a little more expensive one that had like 30 good reviews so I am thinking it should be good. Everything else is working like it should, just the o2 sensors are having issues. What would you think it shows the voltage pretty much just flatlines at .447 volts on both of them. If I command closed loop on the scanner it just keeps on adding fuel, I would guess that if it sees .447 from the o2 sensors it thinks it is lean so it just keeps on adding fuel?

Change the Sensor 1 DTC's back to stock...at least for now. I'll bet you do have a wiring issue. The PCM just can't report it since they have been disabled.

I will give that a shot, I only disabled everything trying to get stuff figured out with my other wiring harness I had. Didn't make any sense to disable everything, I was just trying everything I could think of. It was having a issue with the IAC acting weird with the old harness and the new wiring harness I have now fixed that issue at least.

Well I checked the wiring and it all looks good, I was hoping I would find something. The harness comes with the square plug style o2 sensors which I think are normally the rear o2 sensors from factory, but they have it wired to the pins for the front o2s to the ecu. So that should all still work fine I would think. I also checked the o2s that I have and the heating element works on them. I am going to get a couple new sensors and try those out here soon and see if anything changes.