I also had that exact problem, however, mine resulted from when the two halves of the red connector had separated.
I eventually found that one of the wires inside had broken.
I was able to pick up a DB-9/modular adaptor at a local electronics shop and repaired it.
I probably have my troubleshooting notes around somewhere.
In the meantime, try the cable and computer on a different Ford vehicle if one is available.
Steve
