The header should be able to function without any electronics provided the tractor computer has the header type set manually. Our cord nearly ripped off completely (was dragging on the tire and I didn't realize it) so for a day or two we just ran it unplugged and had to set it in the computer each time the engine was started. So you can unplug it and see if it runs okay. If it runs okay unplugged with the header type set, but not when it's plugged in, it very well could be the cord or plug.
On the D60 all the electronics do is tell the computer what header you have, and provide knife and reel speed sensors (for indexing).