4s-fe Ecu Pinout 【macOS】

The 4S-FE ECU requires stable power. Pin A1 (BATT) keeps the ECU’s memory alive (learned idle, trouble codes). Pin A2 (+B) powers the actual control circuitry. If you lose +B, the engine won’t start. Pins A3 (E1) and A4 (E2) are separate grounds. E1 is for high-current drivers (injectors, ISC), while E2 is for sensor reference. Never combine these without checking the schematic.

| Pin | Wire Color | Signal | Description | |------|------------|--------|--------------| | B1 | B-R | +B | Battery power (EFI main relay) | | B2 | B-Y | +B1 | Battery power (injectors, sensors) | | B3 | B-O | E1 | Power ground (ECU) | | B4 | B-W | E2 | Signal ground (sensors) | | B5 | R | #10 | Injector 1 | | B6 | L | #20 | Injector 2 | | B7 | Y | #30 | Injector 3 | | B8 | L-B | #40 | Injector 4 | | B9 | W | IGT | Ignition timing signal to igniter | | B10 | R-L | IGF | Ignition confirmation from igniter | | B11 | G | G- | Distributor G signal (-) | | B12 | G-R | G+ | Distributor G signal (+) | | B13 | W | NE+ | Distributor NE signal (rpm) | | B14 | B | NE- | Distributor NE signal (-) | | B15 | B-O | STA | Starter signal (from ignition switch) | | B16 | G-W | NSW | Neutral start switch (auto) / clutch switch (manual) | | B17 | R-B | VTA | Throttle position sensor (TPS) signal | | B18 | B-Y | VC | TPS 5V reference | | B19 | G-B | IDL | Idle switch (closed throttle) | | B20 | L-R | PIM | Manifold absolute pressure (MAP) | | B21 | - | - | Not used | | B22 | G-R | FC | Fuel pump relay control | 4s-fe ecu pinout

Don’t buy a scanner. Just use a paperclip. The 4S-FE ECU requires stable power

| Pin | Code | Function | Wire Color | | :--- | :--- | :--- | :--- | | B1 | #10 | Injector 1 (Cylinder 1) | Yellow | | B2 | #20 | Injector 2 (Cylinder 2) | Yellow/Black | | B3 | #30 | Injector 3 (Cylinder 3) | Yellow/Red | | B4 | #40 | Injector 4 (Cylinder 4) | Yellow/Blue | | B6 | FC | Circuit Opening Relay (Fuel Pump control) | Green/Red | | B10 | VS | Air Flow Meter (AFM) Signal | Blue/Black | | B12 | E2 | Sensor Ground | Brown | Don’t buy a scanner

Symptoms: Crank, no start. Check engine light code 12. Fix: Before blaming the distributor, check continuity from pin C1/C3 to the distributor plug. The shielded wire often breaks inside the insulation near the cam timing cover.

If the engine cranks but doesn’t start, the ECU needs NE and G signals.

We will assume the standard 3-plug layout (Plug A = 16 pins, Plug B = 12 pins, Plug C = 14 pins). Looking at the ECU with the harness connector facing you and the locking clip facing up: