2023 GMC Sierra 7500 miles with check engine light issue. Code shows oxygen sensor but dealer says the emission system is not working correctly sending false readings to the oxygen sensor. I’ve taken it back to the dealer six times, twice they kept it for a weak. I pick it up & within two days light comes back on. Anybody got any ideas?

The system doesn't send signals to the sensor it receives them form the sensor. I'd drop it on them and demand they fix their junk.

What is the code?

Are there any other codes? If so, what are they?

What have they done to replicate the issue?

What have they done to fix the issue?

What are your state'* lemon laws?

You already have had it in twice for this issue. Is the third time enough to get them to buy it back?

I'm being a little extreme, but at the same time, this is a warranty issue on a new truck. If they can't fix it, then what is the next step? It sounds like you've been more than understanding.