Self-Test Output/Self-Test Input (STO/STI) Connectors
WARNING: This page is about a different car, the 1989 Ford Probe. However, it is still accessible from the selected car via links, so may be relevant.
The STO connector is a 6-pin connector that is used to perform the Quick Test diagnostic procedure. The STI is a single-pin connector located next to the STO. When the STI is grounded, it activates the ECA fault code output function. Codes are retrieved through the STO connector. Both connectors are located in the engine compartment, behind the driver's side strut tower.