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 engine sensors, relays, and actuators that work together. They provide the car’s Engine Control Unit with vital data parameters essential to govern various engine functions effectively. Generally speaking, Engine sensors are the electro-mechanical devices which monitor various engine parameters. An engine uses different types of sensors. The are Thermo-couples, Resistance Temperature Detectors (RTDs), and Hall Effect sensors.

Various Engine Sensors
Various Engine Sensors

Types of Engine Sensors:

A thermocouple sensor is a temperature measuring device. It converts temperature into the electric charge. Thermo-couples use two different conductors which contact each other at one or more spots. Thus, it produces voltage. It, in turn, sends the signal in the form of electric current to the ECU. Thermo-couples are commonly used as temperature sensors. It measures and controls the temperature such as in the case of Engine Coolant Temperature.



RTDs or Resistance Temperature Detectors also measure the temperature. However, they do so by correlating the resistance of the RTD element with temperature. RTD element is made of pure metals such as the 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 a transducer which varies its output voltage according to the magnetic field. Typically, Hall-Effect sensors detect the speed or velocity. The positioning applications in automobiles use this type of sensor. So, they are used for detecting the Crankshaft speed or its position.



Furthermore, the 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 and ignition timing. It also calculates and supplies the correct amount of fuel to the engine under various load conditions.

A modern-day car has the following Engine Sensors:

SL.

Name of the Sensor

Purpose

01 Air–fuel Ratio Meter Monitors the correct air-fuel ratio for the 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 the engine
05 Cam Position Sensor Monitors  position of valves in the 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/O2/Lambda Sensor Monitors the amount of oxygen in the exhaust
11 Fuel Pressure Sensor Measures pressure in the fuel 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. They include the Ignition Circuit, Spark Plugs, Fuel Injectors, Engine Idling Air Control valve, and Exhaust Gas Re-circulation (EGR) valve. Thus, it extracts the best possible engine performance while keeping emissions as low as possible.

Since all the sensors connect to the ECU, in turn, it can also monitor them for a malfunction. The ECU collects signals from faulty sensors and stores them in its memory. You can diagnose these faults through two methods. Firstly, 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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