Where is the diagnostic plug located for a 1994 ford Taurus GL located?

If memory serves, it should be under the hood either near the right hand side of the firewall, but I might be wrong and it's under the hood near the left fender close to the battery. It should have a black plastic cover which may be labeled 'EEC-TEST'. Not that you cannot use a generic OBDII scan tool, you will need one of the following: NGS scan tool, aftermarket scan tool with US Domestic support, or a multimeter and jumper wire. The multimeter and jumper wire will retrieve codes but not read the data stream as a scan tool will.