Explanation of modern sensors used on modern vehicles
The days of old are gone where a vehicle has a simple 4 stroke combustion engine in it and no regard for the environmental impact it had on the planet. All modern vehicles rely on a computerised system to make sure your vehicles perform as efficiently and environmentally friendly as possible.
I will try to cover and explain as many of the current sensors and their functions. There may be other specific sensors in production but the ones i will cover here are basically standard on all modern cars and light trucks.
First and foremost in the line up would be the ECU also known as either an Engine Control Unit or Electronic Control Unit. This item does exactly as it is named, it controls all of the vehicles engine electronic sensors and tells other parts of the engine how much to compensate for certain circumstances in order to make the engine as efficient as possible. In some cases the ECU also controls many if not all of the interior electric components as well. As long as the ECU is working properly it can read millions of values per second sent to it by the sensors on the vehicle, it then adjusts other electronic parts to compensate and make the vehicle run correctly.
Next we will touch on the Lambda sensors, otherwise known as Oxygen sensors or O2 sensors for short. These sensors are located in the exhaust system itself. The sensor portion itself is located directly in the stream of the exhaust gasses and its sole purpose is to rear the exhaust gas composition and report it back to the ECU. If a lambda sensor tells the ECU then the vehicle is running a bit too lean, the ECU then compensates by allowing more fuel into the engine to richer the mixture, the reverse stands true if the vehicle is running rich to begin with.
The next pair of sensors we will talk about is the MAP or Manifold Absolute Pressure sensor/ MAF Mass Air Flow sensor, the reason we are covering these together is because a vehicle will be equipped with either one or the other, not both. The MAP sensor provides information to the ECU that calculates air density and flow rate, this helps the ECU to figure out if it needs to add more fuel or less to provide optimal combustion. The MAF sensor reads changes in air density as it enters the engine allowing the ECU to determine if more or less fuel is needed for optimum combustion.
The knock sensor is another important sensor on the engine. It’s only function is to listen to the engine and report to the ECU if there is any detonation in the cylinders of the engine. If detonation is present then the ECU varies the ignition spark time either forwards or backwards to compensate and provide optimum combustion.
The coolant temperature sensor is an often overlooked but important sensor in the day to day running of the engine. This sensor reads the temperature of the coolant and makes adjustments to the air and fuel mixture to bring the vehicle up to optimum operating temperature quickly, a faulty coolant temperature sensor can cause many problems, if it is not reading properly the ECU may be telling the engine to add more air and fuel to bring the engine up to temperature when it is already there. Thus making the engine less efficient and wasting fuel. A faulty coolant temperature sensor can also cause the electric cooling fans to either come on to early or too late or even in worst cases not come on at all causing the vehicle to overheat.
Rest assured there are probably many other sensors on your vehicle but the ones listed above are common on all modern vehicles. If you suspect one is not working as it should then please take your vehicle to a qualified mechanic and ask them to run a diagnostic on it, a £50 diagnostic charge now is allot better than the cost of an engine if a fault is ignored.