I am having a similar problem, except that I knew it wasn't a problem with the sensors even if everybody keeps telling me this. P0420 means the catalytic converter is running below threshold efficiency. You might have a car with California emissions even if you don't live in CA. Check on the sticker under the hood, it should tell you. Meineke should have done this if they replaced it for you. If this is the case, you need to get a CA exhaust. I am trying to find one, but it's not as easy as I think it should be. Toyota wanted $1300 for it. Autozone has a federal for about $350, and a CA for about $450. However, the CA doesn't fit on the manifold. Maybe there is another part/pipe that goes to the manifold, or the manifold might be different, but I don't know. Trying to figure this out.
Sorry to hear you wasted money on sensors since they are expensive. I was told that I needed to replace them to, but I got a code reader that records live data, and I could tell it was working and that the sensor was doing what it was supposed to do. It's the cat that's the problem.
Monday, March 23rd, 2009 AT 6:20 AM