4s-fe Ecu Pinout -

These pins receive data from the engine. A faulty connection here results in poor idle, check engine lights, or limp mode.

| Pin Number | Wire Color (Typ) | Function | Description | | :--- | :--- | :--- | :--- | | A- | Red | VC (Voltage Control) | 5V reference voltage for TPS/MAP. | | A- | Light Green | THW (Coolant Temp) | Input from the coolant temperature sensor. | | A- | Yellow | THA (Intake Air Temp) | Input from the IAT sensor. | | A- | Blue | VTA (TPS Signal) | Throttle Position Sensor signal. | | A- | White | NE (RPM Signal) | Signal from the Distributor/Crank Angle Sensor. | | A- | Green/Red | SPD (Speed Sensor) | Input from the vehicle speed sensor. |

If you are pulling a 4S-FE ECU from a junkyard, open the metal casing. Toyota ECUs from this era (early 90s) are notorious for electrolytic capacitor failure. If you see a brown crusty substance on the circuit board, the capacitors have leaked. This can cause erratic sensor readings and phantom check engine lights. 4s-fe ecu pinout

Don’t buy a scanner. Just use a paperclip.

| Test | Between pins | Condition | Expected | |-------|--------------|-----------|-----------| | ECU power | B1 – E1 | Key ON | 11–14V | | Sensor ground | B4 – E1 | Any | < 0.1V | | TPS idle | B19 – E2 | Throttle closed | 0V | | TPS WOT | B17 – E2 | WOT | ~4.5–5V | | MAP (PIM) | B20 – E2 | Ign ON, engine off | ~3.0V (sea level) | These pins receive data from the engine

The ECU sends signals out through these pins to control the engine physically.

| Pin Number | Wire Color (Typ) | Function | Description | | :--- | :--- | :--- | :--- | | A- | Yellow/Red | #10 (Injector 1) | Ground trigger for Fuel Injector #1. | | A- | White | #20 (Injector 2) | Ground trigger for Fuel Injector #2. | | A- | Red/Blue | #30 (Injector 3) | Ground trigger for Fuel Injector #3. | | A- | Green | #40 (Injector 4) | Ground trigger for Fuel Injector #4. | | C- | Green/White | ISC (Idle Speed Control) | Signal to the Idle Air Control Valve. | | C- | Yellow/Black | W (Check Engine Light) | Ground trigger for the dashboard MIL light. | | Test | Between pins | Condition |

(Note: Pin locations A-xx, B-xx, and C-xx denote the specific plug. For example, "Pin 1 on the 26-pin connector" is distinct from "Pin 1 on the 16-pin connector".)

A “crank but no start” condition on a 4S-FE is almost always electrical. Here is a systematic approach using your multimeter and the pinout: