| Pin | Wire Color | Signal | Description | |------|------------|--------|--------------| | C1 | R-B | THW | Engine coolant temp sensor | | C2 | B-Y | THA | Intake air temp sensor (in AFM/MAF) | | C3 | L-R | VS | Airflow meter (AFM) signal | | C4 | R-L | E2 | Sensor ground (return for THW, THA, VS) | | C5 | - | - | Not used | | C6 | G-R | VF1 | O2 sensor feedback monitor | | C7 | W-B | TE1 | Diagnostic request (jumper to E1) | | C8 | B-R | TE2 | Diagnostic test mode | | C9 | L-Y | W | Check engine light (to cluster) | | C10 | G | ACT | A/C compressor clutch relay | | C11 | L-R | IDL2 | A/C idle-up signal | | C12 | R-W | ELS | Electrical load signal (rear defog, etc.) | | C13 | G-B | ISC1 | Idle speed control valve coil 1 | | C14 | B-O | ISC2 | Idle speed control valve coil 2 | | C15 | R | +BM | Backup power (constant 12V for memory) | | C16 | W-B | E1 | Power ground (same as B3) |
Keep this article bookmarked, print the pinout chart, and tape it to your toolbox. When your 1991 Corona won’t start on a rainy morning, you will thank yourself.
The following tables contain based on Toyota's standardized labeling and real-world repair data. Note : Pin numbers and connector arrangements are generalized; your vehicle year and model may vary. Always verify with your specific ECU service number. 4s-fe ecu pinout
Before any electrical test, open the ECU. Look for:
| Pin | Function (Code) | Pin | Function (Code) | | :--- | :--- | :--- | :--- | | A1 | Injector 1 (#10) | A14 | TPS VTA | | A2 | Injector 2 (#20) | A15 | – | | A3 | Injector 3 (#30) | A16 | +B (Main Power) | | A4 | Injector 4 (#40) | A17 | E01 (Power Ground) | | A5 | ISC Solenoid Open (RSO) | A18 | E02 (Power Ground) | | A6 | ISC Solenoid Close (RSC) | A19 | A/C Compressor Relay (ACT) | | A7 | IGT (Igniter) | A20 | Radiator Fan Relay (FAN) | | A8 | IGF (Igniter) | A21 | Check Engine Light (W) | | A9 | – | A22 | Speed Signal Output (SPD) | | A10 | ACIS Control (Optional) | A23 | Fuel Pump Control (FPC) | | A11 | Main Relay Control (MREL) | A24 | E2 (Sensor Ground) | | A12 | EGR Vacuum Modulator (VSV) | A25 | OX1 (O2 Sensor) | | A13 | EGR Temperature Sensor (EGR) | A26 | OX2 (O2 Sensor) | | Pin | Wire Color | Signal |
| Pin Number | Wire Color (Typ) | Function | Description | | :--- | :--- | :--- | :--- | | | White/Red | Battery Constant 12V+ | Hot at all times. Powers ECU memory. | | B2 | Brown | Ground (Case) | ECU chassis ground. | | B14 | Black/Orange | Ground | Sensor/Injector ground. Critical for signal integrity. | | B18 | Black/White | Ground | Main system ground. | | C16 | Black/Yellow | Switched 12V (IGSW) | Power from the ignition key (ON position). |
Intake Air Temperature (IAT) sensor input, typically located inside or near the air filter box. Note : Pin numbers and connector arrangements are
(MAP) sensors are providing steady voltage readings; incorrect data here can cause rich/lean running conditions. Are you currently working on an engine swap or diagnosing a specific fault like a no-start or rough idle? 4E-FE ECU Pinout and Wiring Details | PDF - Scribd
Monitor the PIM and THW voltage signals to ensure the ECU is receiving accurate readings.