cant read codes

[Sandmann43]

I bought a code reader for my 03 6L last year and it worked fine. My EGR caused my CEL to come on again. After I cleaned the EGR I wanted to clear the code, but nothing was there as if it wasnt plugged into the truck at all. I changed the batt and checked the wires nothing. I even used my neighbors reader but it does the same. It drives normal, just cant plug in