On-board diagnostic (OBD) systems monitor the performance of engine and aftertreatment components, especially those responsible for controlling harmful pollutant emissions. The OBD system does not directly measure emissions, but detects system malfunctions that could potentially lead to high emissions. In a practical sense, OBD systems are designed to help ensure proper operation of the vehicle emission control equipment, alerting the driver in case of malfunctions, so that vehicles are properly maintained and meet emissions limits during the lifetime of use.
Given that China is exploring the adoption of OBD requirements for light-duty vehicles (LDV) compatible with future China 6 vehicle emissions regulations for light-duty vehicles, this report takes a closer look at three potential alternatives for OBD regulatory requirements that can be incorporated into the China 6 proposal: Korean OBD II, European OBD Euro 6, and Californian OBD II regulations.
This analysis compares these three OBD programs with respect to technical and regulatory elements. The analysis presents the three programs side by side, exploring similarities and differences on the following main OBD program technical elements: emission control systems monitored, monitoring conditions, OBD emission thresholds, frequency of monitoring, and communication protocols, among others. Also the OBD elements that are relevant to inspection and maintenance (I/M) programs are compared; these elements are designed to prevent fraudulent passing inspections and tampering, improving the effectiveness of I/M programs.
Based on the main findings of this work, the ICCT recommends adopting CA OBDII, including the specific requirements for diesel vehicles, as part of the adoption of China 6 emission standards. The Euro 6 OBD program is not as comprehensive as the Korean and the Californian OBD programs, leaving several emission control systems monitoring requirements open to interpretation. The Korean program is very similar to the Californian OBD program, resulting in similar level of effort for implementation, but its shortcomings on evaluation of communication protocols and treatment of diesel vehicles makes it a less desirable option. Moreover, in light of Volkswagen’s recently admitting to cheating on the U.S. certification of diesel vehicles, and given the growing need to meet fuel consumption standards, a more robust set of regulatory requirements for diesels is needed in all countries, including China. Adopting CA OBDII requirements for China 6 could be phased-in with the new standards, while giving additional time to the implementation of requirements for diesel vehicles. This phase-in time is needed to develop capacity among manufacturers and authorities for developing, adopting and implementing the CA OBD II requirements.
In September 2015, California adopted a set of amendments to its OBD II requirements. Although some of those new requirements are specific to LEV-III emissions standard limits, other provisions relevant to vehicle activity and fuel consumption tracking, as well as access to vehicle data for on-road emission testing with portable systems, could be adopted by China as quickly as possible. The data gathered on vehicle activity and fuel consumption could be used to verify new vehicle fuel consumption information that is used by manufacturers for fuel consumption targets compliance, to improve off-cycle credit assessments, and to better evaluate national CO2 inventories and fuel consumption. Access to data for emission testing with portable systems is a key component of robust compliance and enforcement programs on air-pollution emission standards.