no diagnostic codes readable from scan tool--bad miss and service engine light on 2000 Ford E-150

Two different car parts places scanned my van and received no codes from my system--they thought loose wires under dash (I don't believe it) or a blown fuse for the diagnostic system--I don't know what fuse that would be or how it would be listed

2 answers
A short circuit to any number of sensors can cause problems with data communication line that the scan tool commicates though and simply a bad PCM can cause this. Need to take to good technician to diagnose...parts stores are not going to be able to figure this out for you.
you need a good scan tool to retrive codes at times the cheaper ones are not able to. seek a diag