Warning: Pinouts can vary slightly between different Toyota chassis. A 1990 Corona pinout may differ from a 1992 Carina. Always verify wire colors at the sensor end before cutting or splicing.
This sensor is critical for cold start enrichment. At 20°C (68°F), expect ~2.5V. At 80°C (176°F), ~0.4V. If this wire shorts to ground, the ECU thinks the engine is red hot and will not add fuel on cold start. Unplugging the sensor should default to a safe cold value (~3.0V). 4s-fe ecu pinout
If you have fuel but no spark on a 4S-FE, check the IGT (Ignition Timing Signal) and IGF (Ignition Feedback Signal) pins. Warning: Pinouts can vary slightly between different Toyota