Data Link Connector (DLC) & Self-Test Input (STI) Connector
WARNING: This page is about a different car, the 1995 Ford RV Cutaway, 1995 Ford Econoline, 1995 Ford Cutaway, and 1995 Ford Club Wagon. However, it is still accessible from the selected car via links, so may be relevant.
The 6-pin Data Link Connector (DLC) is used to perform the Quick Test diagnostic procedure. The STI is a single-pin connector located next to the DLC. When the STI wire is connected to SIG RTN terminal of DLC, fault code output function is activated.