Engine sensors in a vehicle are incorporated to provide the correct amount of fuel for all operating conditions. A large number of input sensors are monitored by the engine control unit. Today, sensor technology has become common in modern vehicles. Sensors enhance safety of the people - both on board and on road, control vehicle emissions and make vehicles more efficient. In this article, we will discuss different types of engine sensors used in modern vehicles. The aim of the present textbook was to review the importance of using sensors in automobiles from different points of view which include how fuel injection system works, crankshaft position sensor, cylinder head temperature gauge, internal combustion engine cooling, exhaust gas temperature gauge, idle air control actuator, engine knocking, manifold absolute pressure sensor (MAP), mass flow sensor, nitrogen oxide sensor, oxygen sensor, and throttle position sensor.