2002 Ford Ranger emission question

Hello,

I have a 2002 Ford Ranger with 107000 miles that has been regularly maintained runs smoothly and is in great condition. It has failed inspection because the OBD II can not be accessed via DI connector. It has always worked fine in the past but now when you connect an OBD reader the device (both the garage and I used an Actron) gives an error that the cable must be connected first. I've double tested the connection making sure the leads didn't get pushed back when the cable was connected, check all fuses and all appear in good order. Has anyone had this happen before and can you offer any troubleshooting suggestions? What do the leads from the connector go to? I've not seen a wiring diagram but they appear to all go into a box in the firewall.