4s-fe Ecu Pinout — Link

Do not tap into the VC (A11) pin for aftermarket sensors. That 5V supply is only for the factory AFM and TPS. Use your standalone’s dedicated 5V reference instead.

The 4S-FE ECU requires stable power. Pin A1 (BATT) keeps the ECU’s memory alive (learned idle, trouble codes). Pin A2 (+B) powers the actual control circuitry. If you lose +B, the engine won’t start. Pins A3 (E1) and A4 (E2) are . E1 is for high-current drivers (injectors, ISC), while E2 is for sensor reference. Never combine these without checking the schematic. 4s-fe ecu pinout

: Crankshaft or distributor RPM signals used to determine engine speed and position. Fuel and Air Management Do not tap into the VC (A11) pin for aftermarket sensors

Most 3S-FE ECUs use three main connectors. Let’s label them looking at the harness side (wires facing you). The 4S-FE ECU requires stable power

: Oxygen sensor (Lambda) signal for closed-loop fuel trimming.