Bad engine ground need help!

Okay, heres the low down. I was missing a bolt for holding down the valve cover and it was letting oil into spark plug tubes. So I got the bolt, took cover cleand out the spark plug tubes, got new wires/tubes(NGK) and put cover back on. Then hooked up the ground wire that goes on the valve cover. I had this problem way back before. The ECU throws a Code 15, ignition output signal, last time it was the engine ground on the valve cover, so I sanded it a little and it was fine. But after the other day when I had to take the cover off, I put the ground back on exactly and it gave me hell. So I had some left over wires that I wasnt using from my system, 10guage/8gauge wire, and I made a new ground for the valve cover and it still gives me shit. I mean this thing is grounded like no other, I just don't understand what I'm missing. I need some advice on as what I should try doing. BTW, I figured maybe the cap was bad so I put a new cap/rotor on, I checked the wires on the distributor, coil is good so is the module. And I'll get some pics of the grounds up as soon as I find my digi camera

did you make sure you had both of them connected, cause there is the one on top of the valve cover, then there is another that goes under a nut on the front side of the head

I tried cleaning and sanding the stock ground wire and it still did nothing. I used some old power wire I had left over from my system.

I tried cleaning and sanding the stock ground wire and it still did nothing. I used some old power wire I had left over from my system.

You may also want to check the ground wire that's by the thermostat housing...

Also, did you check the connection of the ground wire at the radiator support? You said you worked on the connections on the valve-cover and the head, but maybe it's on the other end?