P2000 code

I was driving on the highway yesterday when I had to slow down to go around a broken down truck. When I accelerated again it did a quick lag and then a couple seconds later another lag then kicked in but the check engine light came on. Ran fine until I got where I was going. When I restarted it ten minutes later no check engine light and it didn't come back on again. My neighbor works for an auto body shop so brought his scanner over and plugged it in. It gave a P2000 error code. He was able to clear the code.

He said it could mean a number of things: NOx too high in bank 1; faulty solenoid; damaged catalytic converter. I just had an emissions test and I passed with flying colors so he was counting out the catalytic converter as he said it generally doesn't just fail like that and I never would have passed the emissions. Any ideas? The code is so generic and the more I research it the more things it says it can be.