Sensors are mainly used in electronic control systems, such as: electronic control ignition systems and gasoline injection systems. The sensor can detect the physical quantities of the various states and convert the physical quantities Sensor into electricity for delivery. It is like a human sensory organ, the engine under all the conditions of the physical quantity of the correct detection, and enter the control computer circuit. Therefore, the sensor is to determine the engine electronic control system is a key component of good or bad;

       1, speed sensor:

       The speed sensor is usually mounted on a distributor or engine, which detects the corner of the crankshaft. Once the failure, will destroy the ignition system work, so that the engine can not work. As most of the speed sensor is Fuel Rail Pressure Sensor magnetic pulse, it can issue a weak electrical signal, the detection can use a multimeter or oscilloscope;

         A good speed sensor with a multimeter AC voltage file to measure the rotation of the crankshaft, the output voltage should be in the range of 1.5 ~ 3.0V. If there is no AC voltage input or output voltage does not meet the requirements, then the sensor is damaged, it should be replaced;

        When the engine does not turn, the sensor coil resistance check can be carried out. Check the method is to remove the wire plug, with a multimeter resistance file measurement, the resistance should be in the range of 250 ~ 1500Ω;

        If you suspect that the sensor internal wire contact is bad, you can set the multimeter in the resistance file and the sensor wire connected, and then shake the wire to see if the multimeter pointer swing, if the swing that the sensor internal wire contact bad, should be excluded;

       2, knock sensor:

       The knock sensor is mounted directly on the cylinder and is required to have high reliability or stability due to direct temperature changes or vibration on the engine block. Its maintenance tool 'multimeter';

        When the engine is running, connect the sensor wire, slowly increase the speed, and use the multimeter AC voltage file to measure, if the voltage value increases, then the sensor may be faulty;

        When the engine is running, connect the sensor wires, gently tap fuel metering valve the intake manifold with a small hammer, and measure the AC voltage range with the multimeter. If the voltage indication value fluctuates, it indicates that the sensor is faulty;

        Set the ignition switch to the (OFF) position, remove the sensor connector after 10s, and then set the ignition switch to the (ON) position. Measure the DC voltage between the signal output and the circuit terminal on the wiring harness connector. Meet the provisions (specific values ​​please check the maintenance of the vehicle maintenance manual), otherwise the line may be faulty;

    3, water temperature sensor:

     Water temperature sensor is to measure the temperature of the engine cooling water sensor, composed of thermistor, installed in the engine cooling waterway. When the cooling water temperature changes, its resistance changes accordingly. In the electronically controlled fuel injection system, this signal will be input Pressure Sensor to the electronic control unit, you can in accordance with the cooling water temperature correction of the amount of fuel injection. Therefore, the precision of the water temperature sensor has a certain impact on the fuel injection. When the mixture is too thick or too thin, you should first check the water temperature sensor, and then check the other sensors;

        In the inspection, the water temperature sensor can be removed, placed in the teapot for its heating test, measured at different water temperature resistance, the temperature of 20 ℃ when the resistance should be 2 ~ 3KΩ resistance around 80 ℃ Should be 0.2 ~ 0.4kΩ resistance or so.If the measurement results do not meet the requirements, you should replace the water temperature sensor;

       4, intake air temperature sensor:

        The intake air temperature sensor is a sensor for measuring the temperature of the intake air of the engine. The purpose of measuring the intake air temperature is to determine the density of the intake air of the engine and to correct the fuel injection amount in accordance with the change in the air density caused by the temperature change of the intake air. It is usually installed in the air flow meter or air grid after the intake manifold;

       Because of its structure and water temperature sensor is basically similar to the inspection can be used when the water temperature sensor inspection method. Under normal circumstances, when the temperature at 20 ℃, the resistance is about 2 ~ 3kΩ, 60 ℃, the resistance is about 0.4 ~ 0.7kΩ. If the measurement results do not meet the specified requirements, replace the sensor. Replace the air flow meter when the intake air temperature sensor installed in the air flowmeter is damaged;

       5, intake pressure sensor:

       Electronically controlled fuel injection system with speed / density detection of intake air is to use the intake manifold pressure sensor to indirectly measure the amount of air sucked by the engine. Check the supply voltage and output voltage of the sensor normally.

         Check the power supply voltage: Remove the harness connector of the pressure sensor on the intake manifold, set the ignition switch to the (ON) position, and then use the multimeter's voltage range to measure the voltage between the power terminals on the Throttle Position Sensor harness connector. Should be in line with the provisions (specific values ​​please check the maintenance of the vehicle maintenance manual), or should replace or repair its electronic control wiring harness;

       Check the output voltage: Remove the sensor and the intake manifold connected to the vacuum hose, so that the sensor directly connected with the atmosphere, and then set the ignition switch to the (ON) position, with a voltmeter in the electronic control unit harness connector measurement sensor The output voltage, and then to the sensor inside the vacuum, and can be measured under different vacuum its output voltage, the voltage should be reduced with the increase in vacuum density, the changes should be consistent with the technical parameters, or should replace the sensor;

     6, oxygen sensor:

       Oxygen sensor installed in the engine exhaust pipe, the role is to detect the concentration of oxygen molecules in the exhaust pipe, and convert it into a voltage signal or resistance signal, so that the electronic control unit according to this signal to control the concentration of mixed gas;

       Oxygen sensors are heated and non-heated two, for the heating of the heating resistance should be checked;

        Check the heating resistance: use a multimeter to measure the resistance between the two terminals of the heater in its terminal, the normal value should be 4 ~ 40kΩ. Otherwise it should replace its oxygen sensor;

       Oxygen sensor feedback voltage detection: Remove the oxygen sensor harness connector, the voltmeter positive pole test bar directly connected with the oxygen sensor feedback voltage output. Start the engine, the use of a sudden step or relax the accelerator pedal method to change the concentration of the mixture, suddenly depress the accelerator pedal, the mixture is thickened, the feedback voltage should rise; suddenly relax, the mixed gas dilution voltage should be reduced, otherwise the sensor Failure, should be replaced;

        Visual inspection: Remove the sensor from the exhaust pipe, check the ventilation holes on the shell is blocked, whether the broken ceramic core. If damaged should be replaced immediately;

       The engine should be used in the use of high-quality unleaded petrol, its life is usually up to 100,000 km or more, if the use of leaded gasoline is driving a certain mileage, the oxygen sensor will lead 'poisoning' failure