diff light flashing dynatek cdi

Installed a dynatek cdi on a 2002 660 and when I turn on the key the diff light flashes. When I hit the 4×4 button etc it all functions. If I put the factory cdi back on and turn on the key no flashing. Any ideas?
I had the bike apart to adjust valves and change fluids rechecked the connections up front everything looks ok?
appreciate any help.