With the continuous development and popularization of engine electronic control technology, coupled with the rise of vehicle networking, OBD fault diagnosis is becoming more and more familiar. OBD full name: On Board DiagnosTIcs translated into Chinese is: The on-board automatic diagnosis system "OBD II" is "on Board DiagnosiTIcs II", which is the abbreviation of Type II on-board diagnostic system. In order to standardize the diagnosis of vehicle emissions and drive-related faults, since 1996, all new vehicles sold in the United States must have similar diagnostic instruments, fault codes and maintenance procedures, that is, comply with OBD II procedures. As economic globalization and automobile internationalization become more and more high, as a basis for driving and emission diagnosis, OBD II system will be more and more widely implemented and applied.
The OBD II program makes vehicle fault diagnosis simple and uniform, and maintenance personnel do not need to specialize in learning each manufacturer's new system. For example, the OBD system will monitor the car's exhaust gas from the engine's operating conditions at any time. If it exceeds the standard, it will immediately issue a warning. When the system fails, the fault (MIL) light or the 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 fault code, the maintenance personnel can quickly and accurately determine the nature and location of the fault.
The main functions of OBD are as follows:
1. Test the failure of parts and systems at any time to ensure that the vehicle's discharge during service life does not exceed the OBD regulations.
2. When a related emission fault is detected, the OBD system can use the MIL light on the instrument panel to alarm.
3. The faulty vehicle can be repaired in time to reduce vehicle emissions.
4. OBD system helps technicians to diagnose quickly, symptomatic repairs, and reduce maintenance costs.
But for the understanding of OBD, we need to pay attention to: the implementation of the three national standards must be guaranteed by OBDII, but OBDII does not equal these emission standards, OBD has two standards: SAE's US version of OBD, ISO European version EOBD. The time for countries to implement OBD is different. At the same time, there are different versions of OBD, and the functionality varies from version to version.
In addition to various power and ground lines, the key is CAN line, ISO 0141-2 K line, J1850 bus, and there are many interfaces. Let's take a look at the OBDII interface pin definition.
The design of the OBD II program requires avoidance of confusion between systems, which requires not only the use of a standard 16-pin diagnostic interface, but also the use of specific codes and descriptions of the components in the manufacturer's documentation, in order to achieve the following Unification and standardization.
For example, a device that provides crankshaft position and speed information to a computer is referred to as a crankshaft position sensor, abbreviated as "CKP", and the computer is collectively referred to as "PCM."
Each car is equipped with a 16-pin diagnostic interface of standard shape and size. Each pin has the same signal distribution and is located in the same position. It is mounted under the instrument panel, between the left side of the instrument panel and the right 300mm of the center line of the car. At the office. It should be noted that certain terminals of the diagnostic interface are designated as specific signals as shown in the attached table. other terminals are available to the manufacturer or not used on the current model.
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