Oxygen sensor signal tracking air-fuel ratio variance. Actuators & Control
: Crankshaft or camshaft position signals from the distributor for timing. 4A-F Auto to 4A-FE Manual | Page 3 - Toyota Forum
Understanding the expected voltage ranges at each pin is vital. For instance, the THW pin should read approximately 2.5V at 68°F (20°C) and drop below 0.5V when the engine is hot. If a technician measures 5V on the THW pin at operating temperature, the pinout tells them either the sensor is open-circuit or the signal wire is shorted to the reference voltage line (VCC). toyota 4afe ecu pinout
| Pin # | Description | | --- | --- | | 23-35 | Unused or reserved for future use |
| Pin | Wire Color | Function | Signal Type | | :--- | :--- | :--- | :--- | | A1 | Black/Red (B-R) | Battery Power (Constant +12V) | Power | | A2 | Black/Yellow (B-Y) | Main Relay (EFI Relay) Control | Output | | A3 | Black/Orange (B-O) | Injector #4 | Output (Ground switched) | | A4 | Black/White (B-W) | Injector #2 | Output (Ground switched) | | A5 | – | Not used | – | | A6 | Red/Blue (R-B) | ISC Valve (Idle Speed Control) – S1 | Output | | A7 | Yellow/Blue (Y-B) | ISC Valve – S2 | Output | | A8 | Blue (L) | ISC Valve – S3 | Output | | A9 | Yellow/Black (Y-B) | ISC Valve – S4 | Output | | A10 | White/Black (W-B) | ECU Ground (Power ground) | Ground | | A11 | Brown/Black (BR-B) | ECU Ground (Power ground) | Ground | | A12 | – | Not used | – | | A13 | Light Green (LG) | Injector #3 | Output (Ground switched) | | A14 | Light Green/Red (LG-R) | Injector #1 | Output (Ground switched) | | A15 | Red (R) | Check Engine Light (MIL) | Output (Ground switched) | | A16 | Yellow (Y) | Fuel Pump Control (to Circuit Opening Relay) | Output | Oxygen sensor signal tracking air-fuel ratio variance
Working with an ECU requires caution. Here are some important warnings to keep in mind:
| Pin | Wire Color | Signal Name | Function | | :--- | :--- | :--- | :--- | | | Purple | TACH | Tachometer Output (from igniter via ECU) | | C02 | Yellow | NSW | Neutral Start Switch (Auto only) / Clutch switch (Manual) | | C03 | Red/Black | L | Oil Pressure Warning Light (some markets) | | C04 | Black | E2 | Ground for sensors (duplicate of B13) | | C05 | Pink | M-REL | Main EFI Relay Control (ECU turns relay ON) | | C06 | Green/Red | VTA2 | TPS Closed Throttle Position Switch (IDL) | | C07 | Green | VCC2 | Secondary 5V reference (rarely used) | | C08 | - | - | Empty | | C09 | Yellow/Blue | TC | Diagnostic Communication Line (OBD-I scanner) | | C10 | Black/Red | A/C IDL | A/C Idle-Up Signal (raises idle when A/C is on) | | C11 | Red | BATT | Constant 12V for ECU keep-alive memory | | C12 | Yellow/Green | STP | Stop Light Switch Signal (brake pedal input) | For instance, the THW pin should read approximately 2
| Pin | Signal | Wire Color | Description | | :--- | :--- | :--- | :--- | | A-4 | NE+ | (varies) | Crankshaft Position Sensor (NE) Signal+ | | A-5 | NE- | (varies) | Crankshaft Position Sensor (NE) Signal- | | A-13 | E01 | Brown w/ Blue | Injector Transistor Ground | | A-14 | E1 | Brown | Main ECU Ground (also to O2 sensor, data link) | | A-26 | E02 | Brown w/ Blue | Injector Transistor Ground |
I can provide the exact color codes and diagram layout for your specific module. Share public link
The ECU outputs an IGT signal to tell the igniter to fire the coil. Once fired, the igniter sends an IGF pulse back to the ECU. Critical Note: If the ECU does not receive the IGF signal within a few milliseconds of cranking, it will cut fuel injection to prevent flooding, resulting in a "start and immediately stall" condition.