I am guessing that you are going to need to do a resistance check from ground to the different Glow plugs, but I am thinking that your problem is going to be the valvecover gasket, am I wrong here, that is the only harness I can think of???? If you can look in this thread for glow plug wiring, someone posted it about a week ago I think..
The "UVC" or Under Valve Cover harness fail more than a CPS on our trucks. If these fail you will/should receive a code for each and every glow plug on that bank of the engine (either all even codes or all odd numbered codes depending on which side of engine). If I was going through the trouble of pulling the valve covers I would replace the harness with new clips from Ford. The harness is about $25-$30 from ford (x2, 1 for each side) might as well replace glow plugs while your there.