Hi all I,m new to this and im sorry if this question has already been asked.

I have just baught a 55 plate Signum 1.9CDTI auto with 120000 on the clock. For the first couple of day it has run fine if a little sluggish below 2200RPM, then yesterday when joining the moterway and using kick down it went in to limp mode at 4000 ish RPM and the light with a spanner came on. I pulled over and turned the car off then back on and all was fine, until the next time I used kick down! same again. Then today it started doing it when not using kick down but always at 4000 ish RPM. I have had the RAC out and the code he came up with is P0650. Has anyone got any ideas what could be up. Thanks