My girlfriend's 2000 Nissan Sentra has been getting a CEL, so I had her go up to Autozone to have them check it. They told us it was a code P0420 and P1140. I found in my Honda Civic manual that an OBDII P0420 code is a catalyst system efficiency below threshold. It didn't have the P1140 code though. Does anyone know what this is or what might be wrong with the car?

Thanks