I have has the same 02 sensor issues for years. It's bank 2 sensor 2, a few years ago this guy worked on it for months, finally fixed it, said he had to rewire it. A year ago or so the code came up again, both times it was because they sprayed the IAC. So I finally replaced the second one about 2 months ago, code was gone and I got a little more mileage.
A couple weeks ago the engine light went on, it was the same 02 sensor and another, bank 2 sensor 1.
Something about and electrical issue and the remedy was to replace the b2s2. So they did, under warranty, didn't work.
So now they are going through all the wires, this is the second day and say I have to bring it back because they didn't get to all of them.
I wasn't expecting all this and asked how much I was going to be charged, because it's obviously not the sensor.
I'm about to tell him to just bill me and stop the work, I can't pay for all this.
Any ideas what could be going on?