Electrical Load Signal System. Taillight Relay. AC2. Unknown. 12V To Aircon Computer. TE2. White-Blue. Check Connector. TE1. Gray.
You need a 4S-FE specific O2 sensor (1-wire or 4-wire depending on your ECU version). Using the wrong O2 will keep the ECU in open loop and destroy fuel economy. 4s-fe ecu pinout
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. Electrical Load Signal System
A critical safety confirmation signal sent from the igniter back to the ECU confirming that a spark successfully occurred. If the ECU does not detect an IGF signal for a few sequential engine cycles, it will immediately halt the fuel injectors to prevent unburnt gas from flooding the cylinders. Unknown
Keep in mind that ECU pinouts can vary across different models and years, and this information might not be applicable to all 4S-FE engines.
: Sensor ground, used for clean signals from components like the coolant temperature sensor. Ignition System
Frequently features grey plastic connectors with high-density pin layouts.