Ford Bronco EEC Self-Test Connector Pinout Diagram - STO, STI, SIGRTN, Fuel Pump

This document is a simple color-coded diagram identifying the pinout of the Ford EEC diagnostic connectors (the large Self-Test Output connector and the separate single-pin Self-Test Input connector). The larger connector is drawn as a gray multi-pin shape with red highlights marking four terminals, each labeled with its function and corresponding EEC processor pin: SIGRTN (Signal Return) at EEC Pin #46, STO/CEL (Self-Test Output / Check Engine Light) at EEC Pin #17, and Fuel Pump at EEC Pin #22. To the right, a smaller separate single-terminal connector is labeled STI (Self-Test Input) at EEC Pin #48. From this diagram, a reader can learn which cavities in the underhood self-test connectors correspond to which EEC pin functions — information needed to pull diagnostic trouble codes manually (by jumpering STI to SIGRTN), to read codes via the STO/CEL terminal, or to test/power the fuel pump circuit through the diagnostic connector. The image itself contains no year, model, or part number text; it was uploaded alongside 1989 Ford Bronco EEC and fuel system pages and is filed under a 1990 Ford Bronco, which is plausible given the EEC-IV era connector shown.