| Pin | Code | Function | Wire Color | | :--- | :--- | :--- | :--- | | | #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 |
Always cross-reference the OEM part number stamped on your ECU casing (e.g., 89661-xxxxx ) to guarantee exact pin accuracy. Standard 4S-FE ECU Pinout Classifications
If using an aftermarket ignition system, ensure your hardware can mimic the Toyota 12V square-wave IGF feedback signal, or disable the IGF requirement in your software configuration to avoid immediate engine stalling.
Before we dive into the pinout chart, it is essential to understand what you are dealing with. The 4S-FE uses Toyota’s (Toyota Computer Controlled System). Unlike modern CAN-bus systems, the 4S-FE ECU is relatively simple. It relies on analog sensors, a distributor-based ignition system, and a batch-fire fuel injection setup.
Before diagnosing sensor data, ensure the ECU receives proper voltage and has solid ground connections. Without these, the ECU will not boot or communicate with diagnostic tools. 4s-fe ecu pinout
If IGF is missing, the ECU shuts down injectors to prevent catalytic converter damage. If you have spark but no pulse, check IGF .
The ECU used in 4S-FE engines from 1990 to 1996 is the Toyota ECU type " 89661-..." or " 89761-...".
multi-plug configuration. Below are the critical terminals for engine management: Typical Wire Color Function & Connection Black-Yellow Switched 12V power from the EFI main relay. White-Green Constant 12V battery power for ECU memory. Primary computer ground. Brown-White Sensor signal ground. Green / Yellow Injector pulse signals (usually paired 1&3 and 2&4). Black-White Ignition Timing signal sent to the igniter.
| Pin | Type | Signal Name | Function | |:---:|:---:|:---:|:---| | 3 | Input | | Engine Coolant Temperature Signal | | 5 | Input | THA | Intake Air Temperature Signal | | 4 | Input | PIM | Intake Manifold Pressure Signal (for some markets) | | 7-8 | Input | VTA / VCC | Throttle Position Sensor Signal | | 9 | Input | NE | Crankshaft RPM Signal (from distributor) | | 21 | Input | NE (Alt.) | RPM Signal (alternate pin) | | 10 | Input | OX | Oxygen Sensor (Lambda) Signal | | 23 | Input | KNK | Knock Sensor Signal | | 16 | — | E2 | Sensor Ground (return for sensors) | | 24 | Ground | E1 | Computer Ground (main ground) | | Pin | Code | Function | Wire
The 4S-FE uses a simple diagnostic system. Jump pins (B11) to E1 (A3) with the engine off. Turn key ON. The check engine light (pin A15 or B12) will flash codes.
| Pin | Code | Function | Wire Color (Typical) | | :--- | :--- | :--- | :--- | | | +B | Main EFI Relay (Power) | Yellow/Red | | A2 | E1 | ECU Ground (Power return) | Brown | | A9 | STA | Starter Signal (to tell ECU you’re cranking) | Black/White | | A10 | VTA | Throttle Position Sensor (TPS) Signal | Light Green | | A11 | VC | 5V Sensor Power (for TPS & AFM) | Yellow/Blue | | A14 | THW | Coolant Temp Sensor Signal | Brown/Yellow | | A18 | IGF | Ignition Feedback (from Igniter to ECU) | White | | A20 | IGT | Ignition Timing Signal (ECU to Igniter) | Red/White | | A21 | NE+ | Distributor Crank Position Signal (+) | White | | A22 | NE- | Distributor Crank Position Signal (-) | Black |
Manages A/C compressor engagement requests and prompts the ECU to elevate target idle speeds when the compressor cycles on.
: Injector Pulses. Controls the opening of the fuel injectors. typically fires injectors 1 and 3, while fires injectors 2 and 4. Before diagnosing sensor data, ensure the ECU receives
Because these engines were predominantly built for the JDM market, finding reliable English-language wiring manuals can be exceptionally challenging. This comprehensive guide provides a complete breakdown of the 4S-FE Engine Control Unit (ECU) architecture, core pin functions, and practical tips for successful wiring. The Architecture of 1990s Toyota ECUs
Controls the idle air control valve.
The 4S-FE engine is a 1.8L inline-4 cylinder engine produced by Toyota, used in various models such as the Toyota Camry, Corolla, and Solara.
The of the donor vehicle (e.g., 1993 Toyota Corona ST190) The OEM part number printed on the ECU sticker