California HD OBD program—Summary of 2018 amendments
17 December 2018
The California Air Resources Board (CARB) recently approved changes to the Heavy-Duty OBD regulation that included an extensive amount of additional tracking known as REAL Tracking NOx and CO2, as reported last month. This article takes a deeper look into the other changes in the HD OBD regulation (section 1971.1, title 13, California Code of Regulations). The newly adopted amendments and changes are being phased in around the 2022 model year.
An improvement in readability, especially for anyone based outside North America, is that requirements that state a temperature value will now no longer only state it in degrees Fahrenheit but also in degrees Celsius. More improvements or clarifications have been added to the way fault codes and freeze frames are stored or erased. Some of the changes were needed since gasoline engines are now also allowed to use the SAE J1939 protocol for scan tool communication. Another type of readability refers to the MIL itself; if the MIL would be integrated into an LCD screen, it can take the screen a maximum 5 seconds to boot up enough after key-on engine-off to display the MIL.
Any reference to the US EPA CFR is now clarified to be referring to the CFR as it was on January 25, 2018. Changes made by the EPA, therefore, do not automatically influence the CARB OBD regulation.
Concerns existed with the CARB staff that monitors in Heavy-Duty vehicles may not be monitoring often enough in everyday use. One of the steps taken is that monitors designed to run on the SET cycle instead of the more transient FTP will be restricted to only those monitors that must track and report In-Use Monitor Performance data. The number of diagnostics that must track and report In-Use Monitor Performance has increased. Also, the minimum ratio for most monitors is raised from 0.100 to 0.300 which makes it closer to the ratio that applies to Light-Duty vehicles.
Another concern raised by CARB staff was related to intrusive diagnostics. Intrusive diagnostics perform actions that actively influence the monitored system to achieve a better diagnostic result. The fact that intrusive diagnostics are affecting the system can however have an effect on emissions—intrusive diagnostics can cause emissions to increase, as well as to temporarily decrease. CARB added language that states that intrusive diagnostics are not allowed to increase emissions in any reasonable driving condition. The regulation also says that only diagnostics that are a 2nd stage in pinpointing the root cause and run only after a failure was already detected may be of the emissions increasing intrusive kind. Should an intrusive diagnostic enhance (temporarily) the emissions systems effectiveness during any reasonable driving condition, changes in the certification test procedures are likely necessary.
A system of only healing a fault code if the diagnostic confirms that in similar conditions no failure is found again had been in place for Fuel system and Misfire monitors. This method is now expanded to EGR and Boost monitors. This change was motivated by several instances noticed by CARB where a failure was detected in a specific engine operation window, only to heal the fault again when in another window of operation.
One significant element is that the Heavy-Duty regulation now incorporates the same or similar changes as the Light-Duty regulation has already in place for Hybrid vehicles. The rules now explicitly spell out that monitoring must be in place for Energy Storage System itself and the sensors incorporated in it. Monitoring functions now must include Cell-balancing, State-of-Health, State-of-Charge and Thermal management of the battery pack. For the Drive motor and Generator, any failure that can impact the activation/deactivation of emissions control strategies or the operation of the vehicle must be detected. Regenerative braking is mentioned explicitly as well, and so is the Charger in the case it is a Plug-in Hybrid vehicle. Additionally, many definitions and tracking data have changed to be able to cope with Hybrids.
As a portion of the Heavy-Duty Hybrid systems that are in place in North America have been developed separately from the Engine OEM, the clarification of Hybrids in OBD brings them both clarity and even more a need for close cooperation between engine and hybrid system developers.
The Crankcase Ventilation system, a less-known monitor, has been detailed in the sense that the leakage detection must be able to detect a disconnection or damage equal to the smallest diameter hose or tube in the system. Where the priority was before on recognizing if a service technician had forgotten to reattach all hoses after service or repair; the attention is now also to detecting failures.
As the feedgas generation for SCR by the NMHC oxidation catalyst is still difficult to detect and it is difficult to prove that its emission impact is limited, CARB has accepted a window of 30% emissions increase (instead of the 15% that accommodates test-test variations). Variable Valve Timing has also been changed to include Valve lift; to keep up with Variable Valve technologies. These changes already existed in the Light-Duty OBD regulation.
Since NOx sensors play a vital part in the REAL tracking of NOx emissions, additional diagnostics must be added as specified in the regulation. These diagnostics monitor if the NOx sensors would remain stuck in a state of not being active while the engine is operating under conditions where it would be technically feasible to have an active NOx sensor.
The CARB staff has taken action with running changes (requests for approval of changes after certification but when the engine is still in production) and field-fixes (changes after production), at a time where vehicles may get a weekly over-the-air update. CARB is concerned that not all changes are communicated to them and approved before they are released, and that the number of changes could become too much for the staff to handle. Therefore the regulation limits the frequency of changes and details what the change needs to contain and when to request it. Additionally, over-the-air updates can reduce the value of tracking data. The tracking information must be preserved in case of an over-the-air update; if this is not done onboard the vehicle, the manufacturer must first collect the data of all vehicles and then submit a data record to CARB with average and standard deviation per tracking parameter.
The accelerated aging profiles that are used to recreate an engine system representative of full useful life are now described in more detail as CARB found manufacturer proposals to be incomplete. The OBD Demonstration test sequence has been detailed as well to both clarify and to prevent that manufacturers select a sequence that does not correlate well enough to real-world operation. Additionally, during the OBD demonstration manufacturers must also measure and report CO2 emissions. CARB will use the data to determine any future emission thresholds based on CO2.
In the certification documentation manufacturers must also describe all electronic components/systems that are not OBD monitored and the rationale why and under which category of OBD exempt these components/systems are. This forces manufacturers to disclose how for example ADAS systems interact with engine controls. As the vehicle manufacturer typically integrates ADAS systems—of which the engine manufacturer has limited knowledge—this disclosure will require extra effort and agreements with the suppliers. Also, CARB has clarified that they have the authority to request the source code of the software.
The deficiency fines are raised significantly to ensure manufacturers are motivated to prevent deficiencies and to resolve deficiencies in existence quickly. Deficiency fines must be paid for each engine sold in California. The impact of the deficiency determines how much must be paid and there is a limit to the maximum deficiency fine per engine. The first deficiency is for free. Any additional minor deficiencies used to be $25, which is raised to $50. For major deficiencies, the increase is from $50 to $100. The maximum fine per engine is raised in steps from the current $500 to $1500. In addition, specific deficiency categories now exist when a diagnostic exceeds the OBD threshold. For example, for a highest classing deficiency (the OBD threshold is exceeded between 151 and 200%) a fine exists of $400 which is raised in the 3rd model year to $425 and the 4th model year to $450.
Authored by Marcel Romijn & Udaya Kumar, Roben Automotive