Sabisch Michael, Weatherby Meredith, Kishan Sandeep, Fulper Carl
Eastern Research Group, Inc.
U.S. Environmental Protection Agency.
SAE Int J Passeng Cars Electron Electr Syst. 2018;11(1):5-15. doi: 10.4271/07-11-01-0001.
Under contract to the EPA, Eastern Research Group analyzed light-duty vehicle OBD monitor readiness and diagnostic trouble codes (DTCs) using inspection and maintenance (I/M) data from four states. Results from roadside pullover emissions and OBD tests were also compared with same-vehicle I/M OBD results from one of the states. Analysis focused on the evaporative emissions control (evap) system, the catalytic converter (catalyst), the exhaust gas recirculation (EGR) system and the oxygen sensor and oxygen sensor heater (O system). Evap and catalyst monitors had similar overall readiness rates (90% to 95%), while the EGR and O systems had higher readiness rates (95% to 98%). Approximately 0.7% to 2.5% of inspection cycles with a "ready" evap monitor had at least one stored evap DTC, but DTC rates were under 1% for the catalyst and EGR systems, and under 1.1% for the O system, in the states with enforced OBD programs. Monitor readiness decreased, and DTC rates increased, as vehicles aged. DTCs were typically limited to a small subset of all possible DTCs for any particular system. For the on-road versus I/M analysis, lower overall readiness rates and higher overall DTC rates occurred during the roadside test than during the I/M test, and the prevalence of roadside DTCs was shown to decrease around the time of the vehicle's I/M test, possibly indicating some positive I/M influence of reducing on-road DTCs. Roadside Acceleration Simulation Mode (ASM) fail rates also decreased around the time of the I/M test, suggesting a positive influence of I/M programs on reducing vehicle emissions.
根据与美国环境保护局（EPA）签订的合同，东部研究集团利用来自四个州的检查与维护（I/M）数据，分析了轻型车辆的车载诊断系统（OBD）监测器就绪情况和诊断故障码（DTC）。还将路边拦停排放和OBD测试结果与其中一个州同一车辆的I/M OBD结果进行了比较。分析重点关注蒸发排放控制系统（evap）、催化转化器（catalyst）、废气再循环（EGR）系统以及氧传感器和氧传感器加热器（O系统）。Evap和catalyst监测器的总体就绪率相似（90%至95%），而EGR和O系统的就绪率更高（95%至98%）。在配备强制OBD程序的州，约0.7%至2.5%的检查周期中，evap监测器处于“就绪”状态时至少存储了一个evap DTC，但catalyst和EGR系统的DTC率低于1%，O系统的DTC率低于1.1%。随着车辆使用年限增加，监测器就绪率下降，DTC率上升。对于任何特定系统，DTC通常仅限于所有可能DTC中的一小部分。对于道路测试与I/M分析，路边测试期间的总体就绪率低于I/M测试，总体DTC率高于I/M测试，并且路边DTC的发生率在车辆进行I/M测试时有所下降，这可能表明I/M对减少道路DTC有积极影响。路边加速模拟模式（ASM）故障率在I/M测试时也有所下降，表明I/M计划对减少车辆排放有积极影响。
