The 4S-FE utilizes Toyota's TCCS (Toyota Computer Control System). This is an early Electronic Fuel Injection (EFI) architecture. Unlike modern systems that use a Mass Air Flow (MAF) sensor, the 4S-FE primarily relies on a Manifold Absolute Pressure (MAP) sensor to calculate engine load. It also features a distributor-based ignition system with an internal or external igniter and coil.
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. 4s-fe ecu pinout
A thermistor-based signal that changes resistance based on engine temperature. The ECU uses THW to determine cold-start fuel enrichment and radiator fan activation. The 4S-FE utilizes Toyota's TCCS (Toyota Computer Control