Correct me if I'm wrong, but Bank 2 on our cars (both the 3GR-FSE and 2GR-FSE) is on the drivers side? I am suspecting that the harness on this sensor (Sensor 2, the rear one) is not seated correctly which allows water to enter if the undercarriage is sufficiently wetted.

I reached under the car and tried to follow the harness, it appears different than the one on the passenger side and does not enter close to the sensor... the cable seems to disappear under a piece of plastic and I could no longer follow it with my hands with the car on the ground without trying to put excessive force on that plastic. Is that connector only accessible from under the carpeting? Does anybody have any idea how I can get to it to reseat it and check for damage?

I was getting P0158 after driving through some heavily flooded streets. The reason why I suspect the harness and not the sensor itself is because the sensor itself is pretty new it was replaced under a TSB around a year ago and less than 10,000 km. Also, as time passed and the car dried off the codes got set less often and now finally have not seemed to have returned at all (knock on wood). I figure a busted sensor would just keep throwing codes if it wasn't a matter of moisture intrusion in the harness.

At least one dealer around here has quoted me a ridiculous price for the sensor of over $400 (just the part, not even labor). I thought the prices online I saw from US based dealers of close to $150 was bad enough... so I'd really like to just check the harness before making any assumptions about replacement.