2002 GMC Truck Glow plug controller

Electrical problem
2002 GMC Truck 87000 miles

I have a 2002 GMC 3500 bus with a 6.5l diesel I have changed the glow plug controller and I still don't have power going to the glowplugs it is a emissions style controller I have power at the main stud power at the yellow signal wire with key on ground on the black signal wire nothing on the blue and weak ground and the pink signal wire!