October 27, 2021

How to check and repair vehicle sensors

The vehicle sensor is the input device of the automobile computer system. It converts various operating conditions of the vehicle, such as the speed of the vehicle, the temperature of various media, and the operating conditions of the engine, into a signal for transmission to the computer so that the engine is at its best. Working status. Many vehicle sensors, when judging the sensor's failure, should not only consider the sensor itself, but should consider the entire circuit that has failed. Therefore, when looking for a fault, in addition to checking the sensor, check the wiring harness, connectors, and related circuitry between the sensor and the electronic control unit. Let's get to know the main sensors on the car.

Air flow sensor The air flow sensor converts the inhaled air into an electrical signal and sends it to the electronic control unit (ECU) as one of the basic signals for determining fuel injection. According to different measurement principles, it can be divided into rotary vane air flow sensor (Toyota Previa Touring Car), Karman vortex air flow sensor (Toyota Lexus LS400 sedan), hot-wire air flow sensor (Virgo's VG30E engine and domestic Tianjin Sanfeng Bus TJ6481AQ4 equipped with Volvo B230F engine) and hot film air flow sensor four types. The former two are volume flow types, and the latter two are mass flow types. At present, there are mainly two kinds of hot air flow sensors and hot film air flow sensors.

Intake pressure sensor The intake pressure sensor can measure the absolute pressure in the intake manifold based on the load condition of the engine and convert it into an electrical signal and a rotational speed signal to be sent to the computer as a basis for determining the basic fuel injection quantity of the injector. Domestic Audi 100 passenger car (V6 engine), Santana 2000 passenger car, Beijing Cherokee (25L engine), Toyota Crown 3.0 sedan, etc. adopt this pressure sensor. Currently widely used is a semiconductor varistor type intake pressure sensor.

Throttle Position Sensor The throttle position sensor is mounted on the throttle valve to detect the throttle opening. It is linked with the throttle through a lever mechanism to reflect the different operating conditions of the engine. This sensor can detect the different operating conditions of the engine and input it into the electronic control unit (ECU) to control different fuel injection quantities. It has three types: switch contact throttle position sensor (Santana 2000 and Tianjin Sanfeng Bus), linear variable resistance throttle position sensor (Beijing Cherokee), integrated throttle position sensor (domestic Audi 100 V6 engine).

The crankshaft position sensor, also called the crank angle sensor, is the most important sensor in the computer-controlled ignition system. Its role is to detect the top dead center signal, crank angle signal and engine speed signal, and input it into the computer so that the computer can press the cylinder. The firing order gives the best ignition timing command. There are three types of crankshaft position sensors: electromagnetic pulsed crankshaft position sensors, Hall-effect crankshaft position sensors (Santana 2000 sedan and Beijing Cherokee), photoelectric effect type crankshaft position sensors. The type of crankshaft position sensor is different, and its control method and control accuracy are also different. Crankshaft position sensors are generally installed on the side of the crankshaft pulley or sprocket, some are installed on the front end of the camshaft, and some are installed on the distributor (Santana 2000 sedan).

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