This engine temperature sensor monitors coolant temperature and sends a voltage signal to the engine control unit. The ECU uses this signal to adjust fuel delivery, injection timing, and fan engagement for proper thermal management. A failed or drifting sensor can cause incorrect fuel metering, rough running, or an inoperative cooling fan. The sensor threads into the engine block or thermostat housing and uses a standard electrical connector. When replacing, clean the sealing surface and apply thread sealant if specified.