Multimeter (with continuity beeper), 12V test light, a notebook, and an FSM for resistance values.
Do you have a specific 3S-FE pinout question? Leave the year and model in the comments below (or on your favorite forum), but always verify community advice against a factory PDF. 3s-fe ecu pinout pdf
| Pin | Code | Function | Diagnostic Use | | :--- | :--- | :--- | :--- | | C1 | VTA | Throttle Position Sensor Signal | Check for smooth voltage sweep | | C2 | VC | TPS 5V Reference | Must be exactly 5.0V | | C3 | VAF | Air Flow Meter Signal (Karman Vortex) | 3S-FE uses a Karmann vortex AFM | | C5 | OX1 | Oxygen Sensor (Front) | 0.1V (Lean) to 0.9V (Rich) | | C9 | TE1 | Diagnostic Jumper (Check Engine Light) | Connect to E1 to flash codes | | C10 | E1 | Sensor Ground | Do NOT confuse with power ground (E01/E02) | If you cannot find a PDF, or you suspect your harness has been modified, you can reverse-engineer the pinout yourself. This is tedious but foolproof. Multimeter (with continuity beeper), 12V test light, a