If you are working on a vintage Toyota—be it a Corona (ST150/160), Carina (AT190), Celica (ST182/184), or even a Camry (SV25)—the 4S-FE engine is a familiar sight. This 1.8-liter, fuel-injected, inline-4 cylinder engine is legendary for its durability and simplicity. However, as these vehicles approach 30 years old, wiring harnesses degrade, corrosion sets in, and mechanics need to diagnose ECU failures.
Cross-Compatibility: If you cannot find a specific 4S-FE diagram, the 3S-FE wiring from the same year and chassis is almost identical in pin assignment. 4s-fe ecu pinout
, their ECU pinouts are often identical or highly similar, making 3S-FE diagrams a standard reference for 4S-FE troubleshooting. Core ECU Pinout Identification Most 4S-FE ECUs use a 26-pin / 16-pin / 22-pin 4S-FE ECU Pinout: The Complete Wiring Guide for
Diagnostics "Test" terminals. Shorting TE1 to E1 triggers "Check Engine" light flash codes. Speed signal from the instrument cluster (VSS). Starter signal used to enrich fuel during cranking. Throttle Position Sensor (TPS) idle contact signal. Key Differences: 4S-FE vs. 3S-FE While the wiring is nearly identical, the ECU fuel maps Connector 1 (16-pin): Primarily sensors, power, and grounds
+B / +B1: Switched battery power (+12V) via the EFI main relay. BATT: Permanent +12V for memory backup. E01 / E02: Main computer grounds. E1: Engine ground.