car Is running lean? Dealership can’t diagnose the problem? Problem verified

What is your question?

CEL illuminated while at idle waiting at stop sign, started hesitating , jerking and losing power after changing gears. Code reads bank 1 sensor 1-lean dealership has had the car for two weeks and can’t diagnose what is causing the problem. At first it was oil, ruled out, then a fuel sample was sent off, quality came back perfect, the. Ran a days worth of test, no luck, testing for exhaust leaks and attempting to replace gaskets, problem has reoccurred numerous times with the dealership. The mechanic and Nissan technician support are stumped and have yet to figure out why my car is running extremely lean; this condition also caused a pinging from inside the engine bay towards the top of the engine.

What makes this problem better or worse?

When cold the problem doesn’t seem to be as noticeable

How long has your 2019 Nissan Sentra had this problem?

One day before I took it to the dealership