OBDII communication protocol

The communication protocols used by the OBD-II standard are generally: ISO 9141-2, ISO 14230-4 (KWP2000), SAE J1850PWM, SAE J1850 VPM, ISO15765-4 (CAN-BUS). All cars produced in Europe, as well as most cars imported from Asia, use ISO 9141-2 communication protocol circuits. Cars and light trucks produced by General Motors (GM) of the United States use the 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. But now basically use KWP2000.
ISO14230
In the field of automotive fault diagnosis, for the data exchange between diagnostic equipment and automotive ECUs, almost every major automotive company has developed relevant standards and protocols. Among them, a vehicle diagnostic protocol standard widely used in the European automotive field is KWP2000 (Keyword Protocol 2000), which implements a complete set of vehicle diagnostic services and meets the E-OBD (European On Board Diagnose) standard. KWP2000 was originally a diagnostic protocol based on K-line. Due to the limitations of K-line physical layer and data link layer in network management and communication speed, K-line cannot meet the needs of increasingly complex vehicle diagnostic networks. The CAN Network (Controller Area Network) is widely favored in the automotive network field due to its non-destructive network arbitration mechanism, high communication speed (up to 1M bps), and flexible and reliable communication methods. More and more cars Manufacturers use the CAN bus for automotive control, diagnostics, and communications. In recent years, the European automotive field has widely adopted the KWP2000 based on CAN bus, that is, the ISO 15765 protocol, and the KWP2000 physical layer and data link layer protocols based on the K line will be gradually phased out.
ISO15765
The KWP2000 protocol based on the CAN bus actually refers to ISO / WD15765-1 to 15765-4. This protocol transplants the diagnostic services 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 uses the ISO 15765-2 protocol, which specifies the mapping between the network layer protocol data unit, the underlying CAN data frame, and the upper layer KWP2000 service Relationship, and provides synchronization control, sequence control, flow control, and error recovery functions for multi-packet data transmission of long messages.

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