Exhaust gas temperature sensors work to measure the engine temperature which can go as high as 900 degrees Fahrenheit. As the exhaust temperature changes, this part senses it and makes the necessary adjustments. As the temperature increases, resistance is decreased by the sensors. Issues like excessive engine temperatures, vehicle fluid contamination and severe vibration can all cause exhaust gas temperature sensors to become faulty. When this occurs, it can cause symptoms like an illuminated check engine light, engine knock or ping and failing the emissions test. Prompt replacement is important to protect the engine against further damage. If this part is not working properly, the engine is at risk for failure.