Automobile Learning

• Jul 11, 2021
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Information on Automobile Sensors and their functions

Automobile Sensors Used in Trucks

Definition of the sensor:

A sensor is a device that measures a physical variable and converts it into an electrical variable that can be read by an observer/control unit

As this is an engine working with electronic control, there are no. sensors located at various places which give the signal to the ECU. This is called input to the ECU. The ECU is a small computer programmed as per the engine and it takes the signals from sensors, calculates the condition and driver demand (How much accelerator pedal is pressed), and calculates the exact amount of fuel to be delivered per stroke so that the emission norms will get fulfilled after exhaust.

ECU gives the command to FIP, Injectors, and Common Rail and keeps total control of the fuel supply under all conditions. We will see the information about the sensors and how it is attached to the ECU.

1. Air Mass Flow Sensor:

This sensor is fitted near to Air Filter and calculates the flow of filtered air to the intake side. The direction of the sensor is important and is shown by the arrow mark on the sensor.

Principle of operation: It is working on the flow of air and the gauge inside is getting deflected by manifold air pressure. The deflection is measured as a signal. To have only clean air, the passage is made in the sensor which carries out the dust and moisture due to its heaviness.

2. Engine Speed Sensor: This is the same as in BS-III vehicles and is mounted on a flywheel. The flywheel has a teeth wheel with 2 teeth missing.

Resistance is to be checked between pins 1 and 2 and it should be 1050 Ohm +/- 10%.

3. Cam Phase Sensor:

The phase sensor is mounted on a timing cover facing toward the camshaft gear. There is a hole on the camshaft gear which position is sensed. This is based on the hall effect and connected to ECU. The resistance of 570Ohm is to be checked between pins 2 & 3.

4. Rail Pressure Sensor:

Rail Pressure Sensor is mounted on the common rail end and it measures the pressure in the rail and sends the signal to ECU. The ECU varies the fuel supply by opening or closing the MPROP (metering valve on FIP).

5. Coolant Temperature Sensor:

Measurement Principle

The temperature-sensing circuit uses a Thermistor that is sensitive to changes in temperature. It has basically

the NTC (Negative Temperature Coefficient) means as the temperature increases, the resistance decreases.

6. Water In Fuel Sensor :

The Water in Fuel Sensor or WIF sensor indicates the presence of water in the fuel.

It is installed in the fuel filter and when the water level in the water separator Reaches level the WIF sends an electrical signal to the ECU or the dashboard (lamp).

The WIF is used especially in the Common Rail engines to avoid damage.

7. Vehicle Speed Sensor:-

This sensor is a semiconductor device, employing Hall Effect switches. It provides On/Off pulses when a rotating metallic object interrupts the magnetic field.

This sensor takes 12Vdc from the IGN. Supply. The vehicle speed sensor sends output pulses to the Buffer Unit which converts this signal to two buffered outputs one of which is given to ECU and the other to the Instrument cluster Speed indication.