This cylinder head temperature sensor monitors coolant temperature at the hottest point in the engine, the cylinder head. It sends a resistance signal to the engine control unit, which uses the reading to adjust fuel delivery and engage the cooling fan. A failed sensor can cause the engine to run outside its intended temperature range, leading to reduced power, increased emissions, or overheating. The sensor is manufactured to match the original thread pitch and sealing profile of the housing, ensuring a proper seal without additional gaskets. On installation, apply a small amount of thread sealant to the sensor body to prevent coolant seepage.