I have a 2000 Honda crv, the engine light went on and I was told it needed a new Catalytic converter, It was replaced & things were good, when the light came on again they replaced both sensors in front of and behind the converter. I drove the car for one day and the light went back on, now I'm told more sensors need to be replaced. This is getting expensive, I think they're replacing parts hoping to find the problem. The error code is P420 if this helps. Does anyone know what's wrong?