What do you know about OBD Ⅱ?

OBDII (the Second On-Board Diagnostics), the Society of Automotive Engineers (SAE, Society of Automotive Engineers) formulated the OBD-II standard in 1988. OBDII implements standard testing procedures and has strict emission pertinence for real-time monitoring of vehicle exhaust emissions.

Basic introduction

Since the combination of automobile technology and electronic technology in the 1950s, the application range of electronic technology in automobiles has become more and more extensive. As the core of the automobile engine electronic control system, ECU has the characteristics of fast speed, powerful functions, high reliability, and low cost. Therefore, the introduction of ECU has dramatically improved the power, comfort, safety, and economy of automobiles. However, due to the increasingly complex electronic OBDII modular control system of modern engines, the introduction of ECU into the engine electronic control system will not only improve the performance of the car but also cause the problem that the type of failure is difficult to determine. In response to this situation, since the 1980s, automobile manufacturers in the United States, Japan, Europe, and other places began to equip their EFI cars with on-board diagnostics modules (On-Board Diagnostics Module).

The self-diagnostic module can monitor the working status of the electronic control system and its circuit components in real-time during the operation of the car. If there is an abnormality, it can judge the specific fault according to a specific algorithm and use the form of DTC (Diagnostic Trouble Codes) Stored in the car’s computer chip. The useful information obtained after the system’s self-diagnosis can provide help for the repair and maintenance of the vehicle. The maintenance personnel can use the car’s original special instrument to read the fault code so that the fault can be quickly located. After the fault is removed, a special instrument can be used to clear the fault code. Since the OBD systems of different manufacturers during this period were different and incompatible with each other, it was called the First On-Board Diagnostics (OBD-I, the First On-Board Diagnostics). In order to unify the standards, the Society of Automotive Engineers (SAE, Society of Automotive Engineers) formulated the OBD-II standard in 1988. OBD-II implements standard testing procedures and has strict emission pertinence, which is used for real-time monitoring of vehicle exhaust emissions.

OBDII first appeared in several models in 1994, including LEXUS (Lexus) ES300, Toyota Camry (Camry) 1MZ-FE 3.0LV-6 and T100 pickup (light truck), 3RZ-FE Tal 2.7L four-plus AUDI (Audi), Mercedes·Benz (Benz), Volkswagen (Volkswagen) and Volvo (Rich) models. More models were added in 1995, including Nissan Maxima and 240 SX. Then in 1996, U.S. regulations required all new cars and light trucks sold in the country to be equipped with OBD-II systems. Therefore, OBDII systems have been widely installed in new cars and light trucks since 1996.

Working principle

When the car is running normally, the input and output signals (voltage or current) of the electronic control system of the car will change regularly within a certain range; when the signal of the electronic control system circuit is abnormal and exceeds the normal range of change, And this abnormal phenomenon will not disappear within a specific time (3 consecutive strokes), the ECU judges that this part is faulty, the fault indicator light is on, and the monitor stores the fault in the internal RAM in the form of a code ( Random Access Memory: Random Access Memory), the stored fault code can be read by fault indicator or OBD II scanner during maintenance. If the fault no longer exists, the monitor will extinguish the command fault indicator after not receiving the relevant signal three consecutive times. After the fault indicator light goes out, the engine warms up about 40 times, and the fault code will be automatically cleared from the memory.

Protocol

The communication protocols used by the OBD-II standard generally include ISO 9141-2, ISO 14230-4 (KWP2000), SAE J1850PWM, SAE J1850 VPM, ISO15765-4 (CAN-BUS). All cars produced in Europe and most cars imported from Asia use ISO 9141-2 communication protocol circuits. The cars and light trucks produced by General Motors (GM) in the United States use SAE J1850 VPW communication protocol circuit, and Ford (FORD) cars use the SAE J1850 PWM communication protocol circuit.

ISO9141-2

The diagnostic communication protocol proposed in 1994 is forward compatible with ISO 14230-4. The K-line supported by the current OBD port includes the content defined by this protocol. However, KWP2000 is basically used now.

ISO14230

In the field of automotive fault diagnosis, almost all major automotive companies have formulated relevant standards and protocols for data exchange between diagnostic equipment and automotive ECUs. Among them, one of the on-board diagnostic protocol standards widely used in the European automotive field is KWP2000 (Keyword Protocol 2000), which implements a complete set of on-board diagnostic services and meets the E-OBD (European On-Board Diagnose) standard. KWP2000 was originally based on the K-line diagnostic protocol. Due to the limitations of the K-line physical layer and data link layer in network management and communication speed, the K-line cannot meet the needs of the increasingly complex vehicle diagnostic network. The CAN network (Controller Area Network) is widely favored in the field of vehicle networks due to its non-destructive network arbitration mechanism, higher communication rate (up to 1M bps), and flexible and reliable communication methods. More and more cars Manufacturers use the CAN bus for automotive control, diagnosis, and communication. In recent years, the European automotive field has widely adopted the CAN bus-based KWP2000, that is, the ISO 15765 protocol, and the K-line-based KWP2000 physical layer and data link layer protocols will be gradually eliminated.

ISO15765

The KWP2000 protocol based on the CAN bus actually refers to ISO/WD15765-1～15765-4, which transplants the diagnostic service of the KWP2000 application layer to the CAN bus. The data link layer uses the ISO 11898-1 protocol, which is a further standardization and standardization of the CAN2.0B protocol; the application layer uses the ISO 15765-3 protocol, which is fully compatible with the K-line-based application layer protocol 14230-3, And joined the CAN bus diagnostic function group; the network layer adopts the ISO 15765-2 protocol, which specifies the mapping between the network layer protocol data unit (N_PDU, as shown in Table 4) and the underlying CAN data frame, and the upper layer KWP2000 service It also provides synchronization control, sequence control, flow control and error recovery functions for the multi-packet data transmission process of long messages.

Product Features

Now JBO-001, which the OBDII product representative of Jingbang Technology produces, is an intelligent vehicle remote management terminal based on OBD II/EOBD standard protocol. It is a smart device with tracking and remote diagnosis functions. It integrates GPS global satellite positioning technology, and AGPS assisted positioning functions. GPRS global mobile data communication technology and intelligent control technology are integrated, and the volume is minimized. The product is installed on the OBD diagnostic interface of the car, communicates with the car computer continuously, and transmits the real-time car condition and fault information data of the car together with GPS data to the control center through GPRS communication technology and the operator service platform performs analysis, statistics, and storage And show it to users.

OBDII is an on-board automatic diagnosis system, which is a terminal product that detects the operating parameters of the various systems of the car and reads the data. It integrates the inspection, maintenance, and management of automobiles to meet the requirements of environmental protection. The OBD system will separately enter the ECU (computer) of the engine, gearbox, ABS, and other systems to read the fault code and other related data and use a small vehicle-mounted communication system. For example, the GPS navigation system or wireless communication method is used to automatically notify the vehicle’s identity code, fault code, and location information to the management equipment and platform.

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