Ok, sounds like your running to a common problem with the wiring harness. Dont hold me to it but cheak on the passenger side between the transmission and the frame, you will see the O2 sensor rite there. I bet your wireing harness is melted and shorting out. If thats the case, very carfully peel it apart and fix as needed. Do a good job and make sure its water proof or youl get more codes again when its wet. Rerout that part of the harness away from the exaust. It should be done on every VX but it a very neglectid procedere. I even had Isuzu replace it all under warenty and the same thing happened a week later. It also took them 6 months to find it, idiots The factory routing is going the wrong way with that part of the harnes. Also you should disconect the battery before you mess with it. Also find all the plugs you can and put dialectric grease in them, including the ones on your engine. That will take some time but its worth it in the long run.