Principle of operation and purpose of diagnostic parameters
Mass air flow sensor (MAF) located in the air pipe behind the air filter.
The sensor measures the mass flow of air flowing through the inlet pipe to the engine, and an electrical signal is generated in it. Electronic engine control unit (ECM) receives a signal generated by the sensor in the form of a voltage signal, and uses this signal to form 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.
Principle of operation and purpose
Intake manifold air temperature sensor (IAT sensor) built into the intake 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 electronic engine control unit corrects the duration of the injector opening signal (basic fuel injector open time). If the measured air temperature is low, then the electronic engine control unit enriches the air-fuel mixture, increasing the duration of the signal for opening the nozzle. If the measured air temperature is high, then the electronic engine control unit reduces the duration of the signal for opening the nozzle.
Principle of operation and purpose
coolant temperature sensor (ECT sensor) installed in the channel of the cylinder head cooling jacket. The sensor is a thermistor that changes its own resistance depending on the temperature of the engine coolant flowing around the sensor. If the coolant temperature is low, then the sensor resistance is high. If the coolant temperature is high, then the sensor resistance is low. The electronic engine control unit checks the signal voltage of the coolant temperature sensor and, based on the sensor signal, corrects the duration of the injector opening signal and the ignition timing. If the coolant temperature is very low, then the electronic engine control unit enriches the air-fuel mixture (increases the duration of the injector opening signal) and increase the ignition timing (sets early ignition). If the coolant temperature increases, then the electronic engine control unit reduces the duration of the injector opening signal and the ignition timing (sets a later ignition).
Principle of operation and purpose
Throttle position sensor (TPS) mounted on the wall of the throttle body and connected to the throttle shaft. The throttle position sensor is a resistor (potentiometer), which changes its own resistance depending on the throttle position. When the accelerator pedal is depressed, the resistance of the sensor decreases, and when the accelerator pedal is released, the resistance of the sensor increases. The TPS sensor includes a fully closed throttle position switch. The switch closes when the throttle is fully closed. The engine control module supplies control voltage to the throttle position sensor (TPS) and then measures the voltage in the sensor signal circuit. Based on the sensor signal, the electronic engine control unit corrects the duration of the injector opening signal and the ignition timing. Throttle position sensor signal (TPS) along with the intake manifold absolute pressure sensor signal (MAP sensor) used by the ECM to determine the load on the engine.
Principle of operation and purpose
To ensure the lowest concentration of CO (carbon monoxide), NS (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 such a characteristic that its output signal (voltage) changes sharply in the zone of stoichiometric air-fuel ratio. A similar 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 composition of the mixture. 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 (electromotive force at the output of the oxygen sensor is almost 0). If the air-fuel mixture becomes RICHER than the stoichiometric composition of the mixture, the oxygen concentration in the exhaust gases decreases, and the oxygen sensor informs the electronic control unit about the enrichment of the mixture (electromotive force increases to 1 V).
The electronic control unit, in accordance with the magnitude of the electromotive force of the oxygen sensor, determines the degree of deviation of the composition of the mixture from 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 malfunctions, an inadequate signal appears at its output (voltage), the electronic control unit, in this case, cannot execute the proper command to correct the fuel supply. Oxygen sensors are usually equipped with a heater that heats the sensitive zirconium element. The heater is controlled by an electronic control unit. With low intake air flow (exhaust gas temperature is low), the ECU supplies electrical current to the heater, which heats up the oxygen sensor: this ensures an accurate measurement of oxygen in the exhaust gases.
Principle of operation and purpose
When the ignition key is in the position «ON» («On») or «START» («Start»), voltage is applied to the ignition coil. The ignition coil consists of two windings (primary and secondary). High voltage spark plug wires connect the ignition coils to the spark plug of each engine cylinder. Ignition coil causes spark (outbreak) from spark plugs on each working stroke (for the cylinder on the compression stroke and for the cylinder on the exhaust stroke). The first ignition coil causes a spark discharge from the spark plugs of cylinders #1 and #4. The second ignition coil causes a spark discharge from the spark plugs of cylinders #2 and #3. A switch is built into the electronic engine control unit «mass» circuit for turning on the primary winding of the ignition coil. The electronic engine control unit uses the signal from the engine crankshaft position sensor to determine when the winding is turned on. After interruption (on and off) current in the primary circuit of the ignition coil, a high voltage pulse is induced in the secondary winding, which causes a spark discharge from the connected spark plugs.
Principle of operation and purpose
The vehicle speed sensor generates a pulse type signal when the vehicle is moving. The electronic control unit monitors the presence of the sensor output signal.