This is based on the 3S-FE / 4S-FE engine family with a Japanese or European market Toyota ECU (often 22-pin + 16-pin connectors).
⚠️ Note: Pinouts vary slightly by chassis (e.g., ST191, AT210). This is the most common 4S-FE distributor-based, non-VVT configuration.
If you have fuel but no spark on a 4S-FE, check the IGT (Ignition Timing Signal) and IGF (Ignition Feedback Signal) pins.
If you own a 1990s Toyota Corona, Carina, or a JDM import like the Caldina or Celica, chances are you are familiar with the 4S-FE engine. Known for its reliability and balance of torque, this 1.8L inline-four is a workhorse.
However, if you are reading this, you are likely in the middle of an engine swap, diagnosing a "no-start" condition, or tackling a wiring harness repair. When it comes to Toyota electronics, the ECU (Engine Control Unit) is the brain, and understanding its pinout is the map to fixing the nervous system.
In this guide, we will break down the Toyota 4S-FE ECU pinout, identifying the critical pins you need to know for diagnostics and wiring.
| Pin | Code | Function | Wire Color (Typical) | | :--- | :--- | :--- | :--- | | A1 | +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 |
Most 3S-FE ECUs use three main connectors. Let’s label them looking at the harness side (wires facing you).
Toyota changed wire colors over the years. The chart above reflects the most common 4S-FE pinout (1988–1992). However:
Pro tip: Download the specific wiring diagram from Toyota’s TIS or use a quality aftermarket manual (e.g., Haynes #92043) for your exact chassis number.
The 3S-FE ECU is a robust unit from the golden era of Toyota reliability. But 30-year-old wiring gets brittle. Before you blame the ECU, check your grounds and your corrosion.
Print this pinout, tape it to your toolbox, and save yourself three hours of squinting at a blurry PDF.
Got a specific 3S-FE pinout question? Drop your ECU part number in the comments below.
The Toyota 4S-FE is a 1.8-liter inline-four engine known for its reliability in 1990s sedans like the Corona, Carina, and Caldina. If you are performing an engine swap, diagnosing a no-start condition, or installing an aftermarket piggyback controller, understanding the 4S-FE ECU pinout is essential.
Because the 4S-FE was produced across several generations, the wiring can vary between the early "flat plug" OBD1 style and the later "vertical" connector styles. This guide focuses on the common 26-pin, 16-pin, and 22-pin configurations found in early-to-mid 90s models. Understanding the Connector Layout
Most 4S-FE ECUs utilize a three-plug system. When looking at the ECU pins (not the wire side), the plugs are generally labeled from left to right. Plug A (26-pin): Mostly engine sensors and injectors. Plug B (16-pin): Power, ground, and ignition signals.
Plug C (22-pin): Transmission controls and auxiliary signals. Key Power and Ground Pins
Before testing sensors, you must ensure the ECU is receiving power and has a solid path to the ground. 4s-fe ecu pinout
+B and +B1: These are the main power feeds from the EFI relay. They should show 12V when the ignition is ON.
BATT: This is constant 12V power from the battery used for memory. If this wire is cut, your car may run but will lose "learned" idle data every time you turn it off.
E1, E2, E21: These are ground pins. E1 is the main chassis ground, while E2 is a dedicated ground for sensors like the TPS and Coolant Temp.
EO1, EO2: These are power grounds specifically for the high-current injector drivers. Essential Sensor Inputs
If your engine is cranking but not starting, these are the pins you should probe with a multimeter or oscilloscope:
NE+ and NE- (Crankshaft Position): These provide the RPM signal. Without this, the ECU won't fire the injectors or the coil.
G1 and G2 (Camshaft Position): Used for cylinder identification and sequential injection timing.
THW (Coolant Temperature): High voltage here usually indicates a cold engine; low voltage indicates a warm engine. A fault here often causes a very rich or lean condition.
PIM (Manifold Absolute Pressure): The 4S-FE typically uses a MAP sensor rather than an AFM. This pin tells the ECU how much load the engine is under.
VTA (Throttle Position Sensor): Signals the angle of the throttle plate. Output Control Pins
These pins are where the ECU "talks" to the engine components:
#10, #20 (Injectors): These pins ground the injectors to spray fuel. Note that many 4S-FE setups use "batch fire" injection, where injectors are paired.
IGT (Ignition Timing): This is the trigger signal sent to the igniter to fire the spark plugs.
IGF (Ignition Feedback): The igniter sends a signal back to the ECU on this pin to confirm the coil fired. If the ECU doesn't see IGF, it will cut fuel for safety.
ISC (Idle Speed Control): Controls the bypass valve to maintain a steady idle under load (like when the AC is on). Troubleshooting Tips
Check for Voltage at +B: If you have no power at the +B pin, check your EFI fuse and the EFI relay.
Verify Sensor Grounds: Ensure there is zero resistance between the E2 pin and the sensor connectors. A bad ground can cause "ghost" sensor codes.
Check for Spark (IGT/IGF): If you have no spark, check the IGT signal. If you have spark for one second and then it dies, your IGF signal is likely missing. This is based on the 3S-FE / 4S-FE
Note: Always cross-reference your specific ECU part number (e.g., 89661-2Bxxx) as Toyota made subtle changes to wire colors and pin locations depending on whether the vehicle was an automatic or manual, and which specific chassis it was installed in.
For mechanics, tuners, and DIY enthusiasts, understanding the 4S-FE ECU pinout is the cornerstone of successful engine swaps, troubleshooting, and performance tuning. The Toyota 4S-FE, a 1.8L member of the legendary S-series engine family, was a staple in 1990s Japanese domestic market (JDM) sedans like the Corona, Carina, and Vista.
Because the 4S-FE shares much of its architecture with the larger 3S-FE, their ECU layouts are often nearly identical, typically featuring a 26-pin and 16-pin (or 22-pin) connector configuration. Core ECU Pin Functions
The 4S-FE ECU manages everything from ignition timing to fuel injection pulses. Below is a breakdown of the critical pins and their roles in the engine management system. Power & Ground Terminals
Before testing sensors, you must verify the ECU is receiving clean power and has solid grounds. +B and +B1: Switched +12V power from the EFI main relay.
BATT: Permanent +12V feed from the battery for the ECU’s internal memory (Keep Alive Memory).
E01 & E02: Primary computer grounds (usually bolted to the intake manifold or cylinder head). E1: The main internal ground for the ECU logic circuit.
E2: The dedicated sensor ground circuit; never tap into this for high-current accessories. Ignition & Injection Signals
#10 & #20: These pins control the fuel injectors. On the 4S-FE, these are often "batch-fired" in pairs (1 & 3, 2 & 4).
IGT (Ignition Timing): The output signal sent from the ECU to the igniter to trigger a spark.
IGF (Ignition Feedback): A crucial "confirmation" signal sent back from the igniter to the ECU. If the ECU doesn't see IGF, it will cut fuel to prevent catalytic converter damage.
STA (Starter): Informs the ECU the engine is cranking so it can provide a richer fuel mixture for starting. Critical Sensors
PIM (Pressure Intake Manifold): The MAP sensor signal. This is the primary input the ECU uses to calculate engine load and fuel requirements.
THW (Coolant Temperature): Monitors engine heat to adjust fuel trim and idle speed.
THA (Intake Air Temp): Often integrated into the MAP sensor or air box to account for air density.
OX (Oxygen Sensor): Provides feedback on the air-fuel ratio to keep the engine in "closed loop" efficiency.
NE (Engine Speed/RPM): The signal from the distributor or crank sensor that tells the ECU how fast the engine is spinning. Diagnostic Pins: The TE1 and E1 Bridge
On older Toyota ECUs like the 4S-FE, you don't need a modern OBDII scanner to read codes. ⚠️ Note: Pinouts vary slightly by chassis (e
Locate the "Diagnostic" or "Check" connector in the engine bay. Bridge pins TE1 and E1 with a paperclip. Turn the ignition to ON (don't start the engine).
Count the flashes of the "Check Engine" light to read the 2-digit fault codes. Common Wiring Variations
While most 4S-FE engines use a standard Toyota S-series wiring logic, variations exist between early (distributor) and late (distributorless/waste-spark) models. Always verify your specific ECU part number—usually a 10-digit number like 89661-XXXXX—against a Toyota Terminal Guide to ensure you aren't looking at a 4E-FE or 5A-FE diagram, which look similar but have different pin assignments.
Which specific vehicle model or ECU part number are you working with for this 4S-FE project?
You're looking for the ECU pinout for a 4S-FE engine!
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.
Here is the ECU pinout for a 4S-FE engine:
Toyota 4S-FE ECU Pinout ( 1990-1996 models)
The ECU used in 4S-FE engines from 1990 to 1996 is the Toyota ECU type " 89661-..." or " 89761-...".
Here is a basic pinout of the ECU:
Connector 1 (J1, 26 pins)
| Pin # | Signal Name | Description | | --- | --- | --- | | 1 | EGT | Engine Ground | | 2 | IGT | Ignition Timing Signal | | 3 | IGF | Ignition Feedback Signal | | 4 | GND | Ground | | 5 | +B | Battery Voltage | | 6 | THA | Throttle Angle Sensor ( TPS) | | 7 | ODO | Odometer Signal | | 8 | ISC | Idle Speed Control | | 9 | SFT | Shift Solenoid (Automatic Transmission) | | 10 | L | Fuel Pump Relay | | 11 | W | Fuel Pump Monitor | | 12 | RCO | Resistance (Resistor) Check Output | | 13 | NE | Engine Speed Sensor (CKP) | | 14 | NTC | Coolant Temperature Sensor (ECTS) | | 15 | AFS | Air/Fuel Sensor (Oxygen Sensor) | | 16 | A/F | Air/Fuel Mixture Control | | 17 | Rx | Serial Communication Receive | | 18 | Tx | Serial Communication Transmit | | 19-26 | - | Not Used |
Connector 2 (J2, 28 pins)
| Pin # | Signal Name | Description | | --- | --- | --- | | 1 | +5V | 5V Reference Voltage | | 2 | GND | Ground | | 3 | VS | Vehicle Speed Sensor | | 4 | IAC | Idle Air Control Valve | | 5 | ISC2 | Idle Speed Control (auxiliary) | | 6 | F | Fuel Injector 1 ( Cylinder 1) | | 7 | F2 | Fuel Injector 2 (Cylinder 2) | | 8 | F3 | Fuel Injector 3 (Cylinder 3) | | 9 | F4 | Fuel Injector 4 (Cylinder 4) | | 10 | IG | Ignition Coil | | 11 | - | Not Used | | 12-28 | - | Not Used |
Additional notes:
Keep in mind that ECU pinouts can vary across different models and years, and this information might not be applicable to all 4S-FE engines.
Would you like to know more about a specific aspect of the ECU or engine?