Draw the connectors. Count the pins. Note that Toyota ECUs often have missing pins—this is normal.
Multimeter (with continuity beeper), 12V test light, a notebook, and an FSM for resistance values.
If you are reading this, you are likely wrestling with wiring harness gremlins, planning a standalone engine management upgrade, or trying to diagnose a stubborn check engine light on your Toyota. The engine in question is the legendary Toyota 3S-FE —the workhorse 2.0-liter inline-four found in the Camry, Celica, Carina E, MR2 (rarely), and several Coronas from the late 1980s through the 1990s. 3s-fe ecu pinout pdf
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.
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. Draw the connectors
While the 3S-FE is not as performance-oriented as its big brother, the 3S-GE, it is a reliable and durable powerplant. However, age degrades wiring. Corrosion sets in, connectors crack, and sensors fail. Without a , you are essentially navigating a dark room without a flashlight.
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
| Pin | Code | Function | Notes | | :--- | :--- | :--- | :--- | | B1 | #10 | Injector 1 (Cylinder 1) | Switched ground | | B2 | #20 | Injector 2 | | | B3 | #30 | Injector 3 | | | B4 | #40 | Injector 4 | | | B6 | VSV | EGR VSV (Vacuum Switching Valve) | | | B10 | FPU | Fuel Pump Control | |