Check engine light is on

My 01 f350 diesel is reading codes PO676 and PO683. I changed #6glowplug and relay. I reset the computer. The light on back on with PO676 code. How can I fix this.

Try this site and use the search DTC P0676 and DTC P0683. There seems to be some knowledgeable posting there.
http://www.ford-trucks.com/forums/index.php

thank you, I will try this.