Data Link Connector (DLC) & Self-Test Input (STI) Connector
WARNING: This page is about a different car, the 1995 Lincoln Mark VIII. 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.