Another EGR trouble code

2000 Century. A couple of weeks ago I had DTC's read, came up with P0401 EGR Flow Insufficient. By recomendation of a post from this board, I took EGR valve off and checked for plugging. While it was off I cleaned it up some. Replaced EGR valve, had the codes cleared and everything was good. Thanks for the advice.

Yesterday morning I started to drive and SES light came back on. Had codes read today. P0405 EGR Flow, Sensor A Circuit, Low Input. Anyone have any ideas on this code? Please help.

Thanks,