Quote Originally Posted by Scimmia View Post
Are you running a stock cat? If not, many aftermarket cats throw this code all of the time, they just don't work as well as OEM.
I don't think that it's that they don't work as well. I thought it was that they worked "too" well, and the O2 Sensor wasn't seeing enough particles. I would think that it would be illegal to put on a cat that doesn't meet EPA standards, and I'm sure the car manufacturers wouldn't make their cats any more efficient than they needed to be. But I might be wrong.