The Toyota 3S-FE is one of the most reliable 2.0-liter inline-four engines ever built. Produced from the late 1980s through the early 2000s, it powered popular models like the Camry, Celica, RAV4, and Corona. If you are doing an engine swap, wiring a standalone ECU, or troubleshooting an ignition issue, having an accurate electronic control unit (ECU) pinout guide is essential.
Once you have mapped 5 pins (BATT, E1, THW, STA, #10), compare your findings to generic online 3S-FE PDFs. If they match, the rest of the PDF is likely accurate for your car.
When reading a 3S-FE ECU pinout schematic or PDF, look for these standard Toyota terminal designations: Pin Abbreviation Full Name / Function Connected Component Switched Battery Power Main EFI Relay Constant Battery Power Battery (for keeping ECU memory active) E1 / E2 / E01 Ground Terminals Engine Block / Sensor Grounds Injector Pulse Drives Fuel Injectors (Batch fired or sequential) Ignition Trigger / Ignition Feedback Igniter / Ignition Coil pack Engine Speed & Crank Position Crankshaft Position Sensor Camshaft Position Camshaft Position Sensor Throttle Position Signal Throttle Position Sensor (TPS) Intake Pressure or Air Flow MAP Sensor / MAF Sensor Water/Coolant Temperature Engine Coolant Temperature (ECT) Sensor Intake Air Temperature Intake Air Temperature (IAT) Sensor Oxygen Sensor Signal cap O sub 2 Idle Speed Control Idle Air Control Valve (IACV) Accessing Full PDF Pinout Guides 3s-fe ecu pinout pdf
The Engine Control Unit (ECU) is the brain of your engine. The "pinout" is the map that tells you exactly which wire does what. You need this diagram if you are:
Throttle Position Sensor (TPS) outputs indicating throttle angle and idle state. 4. Auxiliary and Diagnostic Pins The Toyota 3S-FE is one of the most reliable 2
Camshaft position signals used to identify cylinder number one for sequential fuel injection.
Auxiliary connector, varying by specific vehicle options like traction control. Critical Pin Assignments & Functions Once you have mapped 5 pins (BATT, E1,
Look at the silver sticker on your physical ECU casing. It will have a 10-digit Toyota part number (e.g., 89661-32020 ). Searching this exact number on enthusiast forums (like ToyoDIY, MR2oc, or regional Camry forums) will often yield exact pinout photos uploaded by other builders.
Sample table layout (for your PDF)
Here are the common reasons for variation:
The ECU requires a stable 12V supply. and +B1 are usually provided by the EFI relay . Ensure E01/E02 are securely grounded to the intake manifold, as poor grounding causes erratic injector behavior. 2. Ignition System (IGT/IGF)