Engine sensors (courtesy: Rotary Electronics)

Engine Sensors: Which Are Different Engine Sensors And How They Work?

What are Engine Sensors?

A modern car’s Engine Management System consists of a wide range of electronic and electrical components. It comprises of engine sensors, relays and actuators. They work together to provide the car’s Engine Control Unit with vital data parameters essential to govern various engine functions effectively. Generally speaking, Engine sensors are electro-mechanical devices which monitor various engine parameters. An engine uses different types of sensors which primarily consists of Thermo-couple, Resistance Temperature Detectors (RTDs), and Hall Effect sensors.

Various Engine Sensors
Various Engine Sensors

Types of Engine Sensors:

Thermo-couples use two different conductors that contact each other at one or more spots which produces a voltage. It, in-turn, sends the signal in the form of electric current to the ECU. A thermo-couple sensor is a temperature-measuring device which converts temperature into an electrical charge. Thermo-couples are commonly used as temperature sensors for measurement and control of temperature such as in Engine Coolant Temperature Sensor.

RTDs or Resistance temperature detectors measure the temperature by co-relating the resistance of the RTD element with temperature. RTD element is made of pure metals such as platinum, nickel or copper. An air conditioning evaporator unit uses this type of probe sensor.

AC Temperature Sensor
AC Temperature Sensor

A Hall Effect sensor comprises of a transducer which varies its output voltage according to the magnetic field. Hall Effect sensors typically detect speed. They are used in positioning applications in automobiles such as to detect the Crankshaft Speed, Position etc.

Furthermore, engine sensors provide the Engine Management System with vital data parameters in real time. These engine sensors continuously monitor the engine parameters. They also provide the ECU with changes that occur in the data from time to time. Based on these inputs, the ECU re-calculates the correct air-fuel ratio, ignition timing and the amount of fuel required by the engine under various load conditions.

A modern day car includes the following engine sensors:


Name of the Sensor


01 Air–fuel Ratio Meter Monitors the correct air–fuel ratio for an engine
02 Engine Speed Sensor Monitors engine speed
03 Throttle Position Sensor Monitors the position of the throttle in an engine
04 Crank Position Sensor Monitors piston’s TDC position in engine
05 Cam Position Sensor Monitors  position of valves in engine
06 Knock Sensor Detects engine knocking because of timing advance
07 Engine Coolant Temperature Sensor Measures the engine temperature
08 Manifold Absolute Pressure or MAP Sensor Used to regulate fuel metering
09 Mass Air Flow or MAF Sensor Notifies the mass of air entering the engine to ECU
10 Oxygen / Lambda Sensor Monitors the amount of oxygen in the exhaust
11 Fuel Pressure Sensor Measures Fuel Pressure in the system
12 Vehicle Speed Sensor (VSS) Measures the speed of a vehicle

Thus, after calculating the fuel quantity, the ECU sends signals to various relays and actuators such as Ignition Circuit, Spark Plugs, Fuel Injectors, Engine Idling Air Control valve & Exhaust Gas Re-circulation (EGR) valve etc. It extracts the best possible engine performance while keeping emissions low.

Since all the sensors connect to ECU, it can also monitor them for malfunction. The ECU collects signals from faulty sensors and stores them in the ECU memory. You can diagnose these faults either by reading the ECU memory with the help of ‘fault codes’ or thru' sophisticated engine diagnostic equipment supplied by the vehicle manufacturers.

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Keep reading: How engine temperature sensor works? >>

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