Unplug the coolant temp sensor. Touch one multimeter probe to the sensor connector terminal and the other probe to an ECU pin. When the buzzer sounds, you have found THW. Mark it.
| Pin | Code | Function | Wire Color (Typical) | | :--- | :--- | :--- | :--- | | A1 | +B | Main EFI Relay Power | Black-Red | | A2 | BATT | Constant 12V Memory | White-Red | | A3 | E1 | Power Ground | Brown | | A4 | IGT | Igniter Trigger Signal | White | | A5 | NE+ | Distributor Crank Signal | Black | | A6 | G1 | Distributor G1 Signal (Cam) | Blue-Red | | A7 | THW | Water Temp Sensor | Green-Blue | | A10 | STA | Starter Signal | Black-White | 3s-fe ecu pinout pdf
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. Unplug the coolant temp sensor
Use a noid light or a low-power LED. Connect it between Battery + and the suspected injector pin (e.g., #10). Crank the engine. If the LED flashes, you found Injector 1. Mark it
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.