I. What is an OBD system?
OBD stands for On Board Diagnostics. It’s a diagnostic system developed for automotive fault diagnosis. “OBD II” stands for “On Board Diagnostics II,” a Type II on-board diagnostic system. To standardize the diagnosis of vehicle emissions and traction-related faults, since 1996, all new vehicles sold in the United States have been required to use similar diagnostic instruments, fault codes, and repair procedures, conforming to OBD II regulations. With increasing economic globalization and automotive internationalization, the OBD II system, as the foundation for traction and emissions diagnostics, will be implemented and applied more widely. The OBD II procedure simplifies and standardizes vehicle fault diagnosis, eliminating the need for repair personnel to learn each manufacturer’s new system.
II. The function of an OBD system
The primary function of an OBD system is to monitor the engine’s operating status and the exhaust gas treatment system’s operational status in real time.
III. The principle of an OBD system
The OBD system continuously monitors the vehicle’s emissions from the engine’s operation to determine if they exceed standards. If they do, it will immediately issue a warning. When a system malfunction occurs, the malfunction indicator lamp (MIL) or the check engine warning light illuminates. Simultaneously, the powertrain control module (PCM) stores the fault information in its memory. The fault codes can be retrieved from the PCM through a specific procedure. Based on the fault codes, technicians can quickly and accurately determine the nature and location of the fault.
The OBD (On-Board Diagnostics) monitors the engine, catalytic converter, particulate filter, oxygen sensor, emission control system, fuel system, EGR, and other systems and components in real time. It then connects to the ECU (Electronic Control Unit), which detects and analyzes emission-related faults, based on information from various emission-related components. When an emission fault occurs, the ECU records the fault information and related codes and issues a warning via the malfunction indicator lamp to inform the driver. The ECU ensures access to and processing of fault information through a standard data interface.