Toyota used the 3S-FE engine across many models and generations (1986–2000). Pinouts vary significantly between OBD-I (pre-1995) and OBD-II (1996+) systems, and between manual/automatic transmissions. Always match the pinout to your exact chassis code and ECU part number.
Comprehensive Guide to the 3S-FE ECU Pinout: Wiring, Troubleshooting, and Resources
Draw the connectors. Count the pins. Note that Toyota ECUs often have missing pins—this is normal.
The 3S-FE was popular in the ST184 and ST204 Celica. Search threads titled "3S-FE ECU pinout" or "Gen2 3S-FE Wiring Diagram." Users have uploaded scanned PDFs to Google Drive. Be extremely cautious: Compare at least three different forum posts to ensure the pins match your car.
For a full schematic including ignition and fuel system integration, the 3S-FE Wiring Diagram includes complete circuit details.
