OBD and other related knowledge[汽车修理知识]

Electronic technology is applied to the engine management system, in addition to basic functions such as fuel injection system and ignition function, there is also an on-board diagnostic (OBD) function. OBD is the abbreviation of On-Board Diagnostics in English, and the Chinese translation is "Automatic On-Board Diagnostics System".
OBD is an automatic diagnosisCarProblem procedure. When the system fails, the fault (MIL) light or check engine (Check Engine) warning light is on, and the powertrain control module (PCM) stores the fault information in the memory, and the fault code can be read from the PCM through a certain program . According to the prompt of the fault code, the maintenance personnel can quickly and accurately determine the nature and location of the fault. Inspect the relevant parts, components and circuits in a targeted manner, and eliminate the fault.
Since the 1980s, major automobile manufacturers in the United States, Japan, and Europe have begun to equip their EFI cars with OBD.Since the OBD systems of major automobile manufacturers are different due to their different engine management systems, each adopts a self-designed diagnostic socket and custom fault codes, and each vehicle series has its own set of special testing tools, such as DedicatedDecoder, Which brings great inconvenience to maintenance and inspection. The initial OBD was unable to self-check its own data, so that the repaired car often failed to meet the technical requirements of the original factory.
An OBD-II which is more advanced than OBD was produced in the mid-1990s. It implements standard inspection procedures and does not require special tools. The Society of Automotive Engineers (SAE) has developed a set of standards and specifications that require all automobile manufacturers to provide a unified diagnostic mode in accordance with the OBD-Ⅱ standard, so that as long as there is one instrument, various automobiles can be tested through a unified socket. For this reason, major automobile manufacturers have changed many aspects of the electronic control system. In the late 1990s, cars entering the North American market were equipped with on-board diagnostic systems in accordance with the new standards.
According to the new standard, the relevant connectors, positions, and codes on the car are all standardized, and no longer do things in different ways. There is a universal standard diagnostic test connector, referred to as DLC. DLC has a 16-pin plug, using standard connectors, the parameters of the car can pass any structure in accordance with the OBD-Ⅱ standardDetectorThe standard installation position of the DLC is under the dashboard on the driver’s side and must be visible; a set of standard terms, abbreviations and definitions are used for all parts of the electronic control system, regardless of what brand of car displays The symbol and meaning of the fault code are the same; the vehicle identification signal can be automatically transmitted to the detection instrument, and can be recorded and stored when the vehicle failsOn-board computerIn the memory, the code can be stored whenever there is a failure that affects the exhaust quality; the testing instrument can delete the failure code stored in the on-board computer memory after the overhaul.
OBD-Ⅱ differs from all previous on-board self-diagnostic systems in that it has strict emission pertinence, and its essential performance is to monitor vehicle emissions.When the emission of HC, CO, NOx or fuel evaporative pollution from the vehicle exceeds the set standard, including the increase in HC emission caused by the engine and its power system randomly, the purification efficiency of the catalytic converter drops below the limit, and the sealedFuel systemThere is an air leak, a certainSensorOr if other emission control devices fail, etc., the MIL lamp will light up and give an alarm. Although OBD-Ⅱ is very effective for monitoring vehicle emissions. But whether the driver will accept the warning when the MIL light is on is another matter. For this reason, an OBD-Ⅲ which is more advanced than OBD-Ⅱ was produced.
The main purpose of OBD-Ⅲ is to integrate the inspection, maintenance and management of automobiles to meet the requirements of environmental protection. The OBD-Ⅲ system will enter the engine, gearbox,ABSThe system ECU (computer) reads the fault code and other related data, and uses a small in-vehicle communication system, such as GPS navigation system or wireless communication, to automatically notify the management department of the vehicle’s identity code, fault code, and location. The management department issues instructions to the vehicle according to the level of the vehicle's emission problem, including recommendations on where to go for repairs, and the time limit for solving the emission problem. It can also issue a prohibition order for vehicles of offenders who exceed the time limit. Therefore, the OBD Ⅲ system can not only warn drivers of vehicle emission problems, but also punish violators.
Che Huitong

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