Coolant Temp Sensors Offer superior coverage for Import / Domestic applications Manufactured with the highest quality materials according to rigorous standards for superior performance and durability 35 Numbers in stock Imported and Domestic vehicles Coverage Find a retailer The Coolant Temperature Sensor, also known as the coolant temperature switch, is an engine management system sensor that is used to monitor the temperature of the engine coolant. Most coolant temperature sensors operate using electrical resistance to measure the temperature of the coolant. This signal is then sent to the electronic control unit (ECU) so that changes can be made to the engine’s timing and air/fuel mixture for optimal performance, as engines require more fuel when they are cold, and less fuel when they are fully warmed up. The computer will also scale back engine performance settings if it detects that the engine temperature is too high to protect the engine from possible damage due to overheating. Because temperature plays such a vital role in engine performance calculations, a problem with a coolant temp sensor can quickly translate into engine performance issues.