Contents: Operating principle and purpose of…⇓ Operating principle and purpose ⇓ Operating principle and purpose ⇓ Operating principle and purpose ⇓ Operating principle and purpose ⇓ Operating principle and purpose ⇓ Operating principle and purpose ⇓
Operating principle and purpose of diagnostic parameters
The mass air flow (MAF) sensor is located in the air duct behind the air cleaner.
The sensor measures the mass flow of air flowing through the intake manifold to the engine, and in doing so, it generates an electrical signal. The engine control module (ECM) receives the signal generated by the sensor as a voltage signal and uses this signal to generate the basic duration of the injector control signal and the ignition timing.
As the mass air flow increases, the voltage generated by the sensor increases.
Operating principle and purpose
Intake Manifold Air Temperature Sensor (IAT sensor) built into the manifold absolute pressure sensor (MAP sensor). The sensor is a resistor that changes its own resistance depending on the temperature of the air entering the intake manifold. Based on the sensor signal, the engine control unit adjusts the injector opening signal duration (the basic open time of the fuel injector). If the measured air temperature is low, the engine control unit enriches the air-fuel mixture, increasing the injector opening signal duration. If the measured air temperature is high, the engine control unit reduces the injector opening signal duration.
Operating principle and purpose
Coolant temperature sensor (ECT sensor) is installed in the cooling jacket channel of the cylinder head. The sensor is a thermistor that changes its own resistance depending on the temperature of the engine coolant flowing near the sensor. If the coolant temperature is low, the sensor resistance is high. If the coolant temperature is high, the sensor resistance is low. The engine control unit checks the voltage of the coolant temperature sensor signal and, based on the sensor signal, adjusts the injector opening signal duration and the ignition timing. If the coolant temperature is very low, the engine control unit enriches the air-fuel mixture (increases the injector opening signal duration) and increases the ignition timing (sets early ignition). If the coolant temperature increases, the engine control unit reduces the injector opening signal duration and the ignition timing (sets late ignition).
Operating principle and purpose
The throttle position sensor (TPS) is mounted on the wall of the throttle body and connected to the throttle shaft. The throttle position sensor is a resistor (potentiometer) that changes its own resistance depending on the position of the throttle valve. When the accelerator pedal is pressed, the sensor resistance decreases, and when the accelerator pedal is released, the sensor resistance increases. The TPS sensor includes a fully closed throttle position switch. The switch closes when the throttle valve is fully closed. The ECU supplies a control voltage to the throttle position sensor (TPS) and then measures the voltage in the sensor signal circuit. Based on the sensor signal, the ECU adjusts the injector opening signal duration and the ignition timing. The throttle position sensor (TPS) signal, along with the manifold absolute pressure (MAP) sensor signal, is used by the engine control unit to determine engine load.
Operating principle and purpose
To ensure the lowest concentration of CO (carbon monoxide), HC (unburned hydrocarbons) and NOx (nitrogen oxides) in the exhaust gases, a three-way catalytic converter is used. For more efficient use of the catalytic converter, the fuel supply system must prepare a working mixture of a certain composition called stoichiometric. The oxygen sensor has a characteristic in which its output signal (voltage) changes sharply in the stoichiometric air-fuel ratio zone. Such a characteristic is used to determine the oxygen concentration in the exhaust gases and, in the form of feedback, sends a signal to the electronic control unit to adjust the mixture composition. If the air-fuel mixture becomes LEAN, the oxygen concentration in the exhaust gases increases and the oxygen sensor informs the electronic control unit about this with a corresponding signal (the electromotive force at the oxygen sensor output is almost equal to 0). If the air-fuel mixture becomes RICHER than the stoichiometric composition of the mixture, the concentration of oxygen in the exhaust gases decreases, and the oxygen sensor informs the electronic control unit about the enrichment of the mixture (the electromotive force increases to 1 V).
The electronic control unit, in accordance with the value of the electromotive force of the oxygen sensor, determines the degree of deviation of the mixture composition from the stoichiometric and, in accordance with this, adjusts the required amount of injected fuel by changing the duration of the injector control signal. However, if the oxygen sensor is faulty, an inadequate signal (voltage) appears at its output, the electronic control unit, in this case, cannot execute the proper command to adjust the fuel supply. Oxygen sensors are usually equipped with a heater that heats the sensitive zirconium element. The heater is controlled by the electronic control unit. At low air flow rates at the intake (the exhaust gas temperature is low), the electronic control unit supplies electric current to the heater, which heats the oxygen sensor: this ensures the accuracy of measuring oxygen in the exhaust gases.
Operating principle and purpose
When the ignition switch is in the "ON" or "START" position, voltage is supplied to the ignition coil. The ignition coil consists of two windings (primary and secondary). High-tension spark plug wires connect the ignition coils to the spark plug of each engine cylinder. The ignition coil causes a spark discharge (flash) from the spark plugs on each power stroke (for a cylinder on the compression stroke and for a cylinder on the exhaust stroke). Ignition coil 1 causes a spark discharge from spark plugs of cylinders #1 and #4. Ignition coil 2 causes a spark discharge from spark plugs of cylinders #2 and #3. A ground switching circuit is built into the ECM to turn on the primary winding of the ignition coil. The ECM uses the signal from the engine crankshaft position sensor to determine when to turn on the winding. After interrupting (switching on and off) the current in the primary winding circuit of the ignition coil, a high voltage pulse is induced in the secondary winding, which causes a spark discharge to appear from the connected spark plugs.
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Operating principle and purpose
The vehicle speed sensor produces a pulse-type signal when the vehicle is moving. The electronic control unit monitors the presence of the sensor output signal.