Turn the ignition off. Find the thickest white-red wire (BATT). It should have 12V constant. Find the thick brown or white-black wires (E01, E02). These are high-current grounds for injectors.
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
Multimeter (with continuity beeper), 12V test light, a notebook, and an FSM for resistance values. Turn the ignition off
Draw the connectors. Count the pins. Note that Toyota ECUs often have missing pins—this is normal. 12V test light
Turn the ignition off. Find the thickest white-red wire (BATT). It should have 12V constant. Find the thick brown or white-black wires (E01, E02). These are high-current grounds for injectors.
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.
Multimeter (with continuity beeper), 12V test light, a notebook, and an FSM for resistance values.
Draw the connectors. Count the pins. Note that Toyota ECUs often have missing pins—this is normal.
