• Service Information Current: Since the start of OBD II, manufacturers have been required to make available service information necessary to use the OBD II system to repair vehicles.

  Future: Beginning January 1, 2002, manufacturers will have to make the info available in a standardized electronic format. Many OEMs are already moving toward electronic information, but in a proprietary format. (For example, to use GM information you need special GM software to read the CD-ROM data files, etc.) Starting in 2002, manufacturers would have to put the information in an SAE standardized format so a single software program could be used to look at any OEM's service information. As a side note, if the EPA's service rule goes through and requires availability through the Internet, CARB will probably accept Internet capability as equivalent to putting the information in this SAE standardized format since any technician with a Web-browser would have access.

• Catalyst Monitoring Present: The current OBD II regulation requires monitoring of the catalyst for malfunctions affecting hydrocarbon conversion efficiency. This is accomplished through pre- and post-catalyst oxygen sensors. These sensors are simply monitoring the catalyst's ability to absorb oxygen.

  Future: Data from OBD II demonstration vehicles show that NOx emissions can be high when HC emissions reach the malfunction threshold. This means that a way of monitoring NOx emissions is coming! To maximize NOx emission reductions, CARB is proposing a NOx-based catalyst monitoring requirement for vehicles in addition to the HC-based requirement. Monitoring technologies, such as the use of a NOx sensor, might be used to meet this proposed requirement. Another method is to evaluate the light-off characteristics of the catalyst using a catalyst temperature sensor. CARB proposes that the NOx efficiency monitoring requirement be phased in with the introduction of vehicles meeting the LEV II standards (2004-2007). The most likely method (expected way for all manufacturers to meet this requirement) is to continue to use dual O2 sensors and monitor the ability of the catalyst to store and release oxygen. This dictates the ability of the catalyst to convert HC or NOx emissions.

• Misfire Monitoring Present: Manufacturers have expressed concerns about MIL illumination for misfire rates below 1.0 percent. At such low levels, the probability of false MIL illumination increases and misfire levels of 1.0 percent or less may be difficult to diagnose.

  Future: Misfire monitors are sensitive; a car misfiring for a minute or two can be enough to turn on the MIL and it can be difficult to recreate that actual misfire and repair. To address this sensitivity, CARB changed the requirement from exceeding the misfire rate for any one 1000 rev block to any four 1000 rev blocks in a single driving cycle (i.e., the misfire has to be around for four times as long as it used to be). The '96, '97 and some '98s use any 1000 rev block while most '98 and newer models use any four 1000 rev blocks.

• Cold Start/Warm-up Strategies Present: A significant portion of the weighted emissions of an FTP test for low emission vehicles is generated during the first two minutes of the cold start portion of the test. In developing vehicles to meet LEV standards, some manufacturers have used a variety of engine calibration techniques to reduce cold start emissions and accelerate catalyst light-off. These techniques include ignition retard, increased idle speed after engine start, and richer or leaner than stoichiometric air-fuel mixtures.

  Future: With the accelerated catalyst light-off strategies, the idle speed control system must function properly during cold conditions to achieve the emission standards. If higher idle speed cannot be achieved due to a fault that is present only during cold operation (such as a sticking or slow idle air control valve), catalyst light-off will be delayed, and emissions can be excessive with no indication to a driver or repair technician. Therefore, CARB believes that confirmation of the accelerated warm-up conditions is necessary.

  There is a proposed requirement to monitor the engine operating conditions such as engine speed, air/fuel ratio and ignition timing to verify that the commanded conditions were achieved. The regulatory language would thus specify that the emission/engine control system shall be monitored for achieving the required engine operating conditions necessary for accelerated catalyst warm-up. A manufacturer may develop a diagnostic strategy using catalyst temperature sensors to verify that the conditions to accelerate catalyst light-off were achieved or catalyst light-off temperature was reached within a specified amount of time.

• Evaporative System Leak Detection Present: Current regulations require monitoring of any evaporative fuel system leaks that exceed .040 inch in diameter (approximately 1 millimeter).

  Future: Beginning in the 2000 model year, manufacturers are required to phase in monitoring for small leaks equal to or greater in magnitude than a 0.020 inch diameter orifice. Full compliance with the 0.020 inch requirements on all vehicles is scheduled to take place in the 2003 model year. Manufacturers are performing the 0.020 inch diameter leak check of the fuel and evaporative control system using either a vacuum or pressure strategy. Under both of these methods, the pressure inside the system is monitored over an interval of time. If the pressure or vacuum changes toward ambient at a significant rate, a leak is considered to be present. Between the two methods, pressure-based technologies are generally more reliable in detecting a 0.020 inch leak and have a lower probability of signaling false malfunctions. Therefore, to reliably detect a 0.020 inch diameter leak under reasonable monitoring conditions, vacuum-based technologies must set the malfunction threshold at a level significantly lower than 0.020 inch (maybe as low as 0.015 inch) while the pressure-based technologies can set the threshold at a level closer to 0.020 inch. Unlike the vacuum-based check where ambient air enters the system when the monitor is operating and a leak is present, a pressure check causes the air-vapor mixture in the evaporative control system to be expelled from the system when any size leak is present. In other words, performing the pressure check causes increased evaporative emissions to be released to the ambient if a leak is present. If there is a leak equivalent to or larger in magnitude than 0.020 inch present, then the leak is identified and fixed. However, if there is a leak smaller than 0.020 inch present, then the pressurized leak check would not identify the leak, but in the process of performing the check, excess evaporative emissions would be generated.

• Fault Codes Present: Fault codes provide technicians with detailed information necessary to diagnose and repair vehicles in an efficient manner. The standardized fault codes listed in SAE J2012 include a number of fault codes for each component or system. In the fault code listing, there is usually a “general” fault code that indicates a fault with a particular component or system (e.g., P0100 Mass or Volume Air Flow Circuit). There are also additional, more specific, fault codes for the different failure conditions of the same component/system (e.g., P0102 Mass or Volume Air Flow Circuit Low Input, or P0103 Mass or Volume Air Flow High Input).

  However, some manufacturers only use general fault codes to simply indicate the component or system that is malfunctioning. The repair technician is then required to use the manufacturer's service information or a fault tree to pinpoint the problem. In many cases, the diagnostic system actually detects different root causes (e.g., sensor shorted to ground or battery) for a malfunctioning component/system, yet the manufacturer only uses one fault code to identify all the different malfunctions.

  Future: Many codes are designated with a P1xxx format as opposed to the generic, SAE-defined fault codes of P0xxx. Because these codes are manufacturer-defined, generic scan tools are unable to display the text label that corresponds to the fault code. Thus, technicians are only given the numeric fault code and a message such as “manufacturer-defined fault code.” CARB is seeking industry feedback to ensure that the majority of technicians have reasonable means available to identify the fault associated with a P1xxx fault code.

  Similar to the practice described above, some manufacturers use limited fault codes to only indicate the malfunctioning component or system. More detailed fault information or analysis, known as symptom bytes, is then provided through a manufacturer-specific scan tool or “dealer” tool. In this situation, the dealer technician is provided with electronic information that is not available through the generic scan tool. If the information is available in the diagnostic system and useful to a dealer technician, the information must be provided to the generic scan tool.

• Oxygen and Air/Fuel Ratio Sensor Monitoring Present: Most manufacturers use the rear (secondary) oxygen sensor for fuel control or to “trim” or correct the output from the front (primary) oxygen sensor. The rear sensor can be used to correct the front sensor for aging, poisoning or deterioration resulting in offset or drift. Some manufacturers set limits on the correction by the rear sensor and, when the limits are exceeded, store a fault code and illuminate the MIL.

  Future: The diagnostic system may monitor the output voltage, response rate, primary oxygen sensor correction (if applicable), and other parameters that can affect emissions, of all primary (fuel control) oxygen (lambda) sensors for malfunction. It shall also monitor all secondary oxygen sensors (fuel trim control or use as a monitoring device) for proper output voltage and response rate. Response rate is the time required for the oxygen sensor to switch from lean to rich once it is exposed to a richer than stoichiometric exhausts gas or vice versa (measuring oxygen sensor switching frequency may not be an adequate indicator of oxygen sensor response rate, particularly at low speeds). This means that the vehicle will now be performing the “rate of change” test that we've been doing with our lab scopes.

• PCV Monitoring Future: Beginning with the 2002 model year, manufacturers will phase in diagnostic strategies to monitor the PCV system, which will be required by the 2004 model year. The malfunction criteria for a PCV valve will be as follows: The PCV system shall be considered malfunctioning when disconnection occurs between either the crankcase and the PCV valve, or between the PCV valve and the intake manifold. Monitoring Conditions: The monitoring system will operate at least once per driving cycle during which the manufacturer-defined monitoring conditions are met.

  The diagnostic system will store a fault code and the MIL shall illuminate no later than the end of the next driving cycle during which monitoring occurs provided the malfunction is again present.

Inspection and Maintenance Program Issues For more information...

• Automotive Service Association: www.autoinc.org (search for additional articles on this topic)
  
• California Air Resource Board: arb.ca.gov (type “OBD” in the search box)
• Environmental Protection Agency: epa.gov
• General Motors 'Flash' information: calid.gm.com/vci/
• International Automotive Technician Network: www.iatn.net
• Service Technican's Society: sae.sts.org
• Society of Automotive Engineers: sae.org

Currently, inspection and maintenance (I/M) programs are being reviewed and, in some instances, being restructured to incorporate OBD II system checks as a primary element of the program. There has been considerable discussion among industry and government agencies on the issue of readiness indications for I/M testing. The intent of the readiness indications is to ensure that a vehicle is ready for testing (i.e., all the major monitors have run). Readiness indications are a significant component of the OBD II system. Readiness indications were incorporated into the OBD II requirements to address problems with I/M testing on OBD I vehicles. This ensures that the vehicle has been driven sufficiently for the OBD II system to test all the emission control components and determine whether or not a fault is present. Second, readiness indications also combat fraud in I/M testing. It was possible with OBD I vehicles to erase fault codes just before a vehicle was subject to the I/M test, thus enabling a malfunctioning vehicle to falsely pass an I/M test. If fault codes are erased on an OBD II vehicle, the readiness indications are set to incomplete at the same time. If a fault remains, it will be detected again before all readiness indications are set to complete. Therefore, it is important for all readiness indications to be complete before subjecting a vehicle to an I/M test.

As OBD II checks are added to I/M tests, there is concern that a significant portion of vehicles would be rejected for an I/M test because they do not have complete readiness indications for all major monitors. And what about consumer reaction should even small numbers of vehicles with incomplete readiness indications be rejected in an OBD II-based I/M program? Data from pilot I/M test programs show approximately 2 percent of test vehicles have incomplete readiness indications. An analysis of the data shows a large portion of the incomplete readiness indications are for the evaporative system monitor.

In Davis County, Utah, 65,927 vehicles were tested between January 1997 and July 1999. Of these, 91.33 percent tested “good,” 4.76 percent tested “not ready,” 2.26 percent had DTCs, .74 percent had their MIL on, and 1.48 percent were unable to communicate.

Doug Decker of the Colorado Department of Public Health and Environment referred to a DCPHE study to explain his views on the effectiveness of OBD II as a tool for identifying emission failures. The study states: “The results of this study indicate that OBD II is a very effective strategy for identifying vehicles with either high emissions or potentially high emissions. However, the data generated from this study indicate that if OBD II MILs alone were used to predict FTP pass/fail, the false identification rate would be 60 percent; i.e., 21 of the 35 study vehicles that failed OBD II (MIL illuminated) passed the FTP.”

A second way of looking at OBD II is to determine if the stored DTCs actually identify an abnormality. For regular-mileage vehicles, OBD II DTCs identified system or component problems that were in need of repair or that could have eventually resulted in high emissions 94 percent of the time (30 of 32 vehicles). For high-mileage vehicles the identification rate was 67 percent (six of nine vehicles). Using this criterion, OBD appears to be a reliable tool with which to identify high emitters or potentially high emitters. However, when OBD II DTCs indicated component or system problems, 18 of the 31 identified regular mileage vehicles and five of the seven identified high mileage vehicles passed the FTP. As a result, the DTC false identification rates with regard to federal In-Use FTP standards were 58 percent and 71 percent for regular and high mileage vehicles respectively.

Decker emphasized a problem scenario - a vehicle that failed OBD II for a lit MIL in the I/M station. “This vehicle is now in your shop for repair, and its emissions levels are cleaner than when it was new; and approximately 10 times cleaner than the I/M standard,” said Decker. “There is a problem with the car, but it may cost the motorist $400 or more for a negligible emissions reduction (and likely no change to driveability or fuel economy).”

There are a number of reasons why readiness indications may not be set at the time of inspection. If a vehicle with the MIL illuminated was repaired shortly before an I/M test and had fault codes cleared subsequent to the repair, the vehicle may not have been driven sufficiently to exercise all of the major monitors before being taken to the I/M station. In some cases, vehicle operation in extreme ambient conditions will prohibit the monitors from running and setting readiness indications.

“When a tech repairs an OBD II problem and clears codes, the readiness monitors need to be reset before the car can be retested. Who will do this? ... It may take a couple of days of 'normal' driving to reset monitors,” said Decker. “What about the procrastinator whose registration expired yesterday and is now driving around trying to reset monitors and gets a ticket? Will the motorist see the tech's unwillingness to reset monitors as poor service? Supposedly, some manufacturers have already established a key cycle test that flashes the MIL to indicate whether the monitors are set or not. Service advisors will need to have a script to work from - like an FAQ - when dealing with OBD II and MILs,” Decker added.

In summary, a statement from the CARB Web site appropriately addresses the status of OBD II:

“One of the primary goals of the OBD II program is, and always has been, to improve the availability of service information to the aftermarket repair industry. As such, the OBD II regulation contains several requirements for standardization of diagnostic connectors, communication protocols, fault codes, engine parameter data and test equipment. Additionally, staff has proposed new amendments improving the availability of diagnostic and repair information for all emission-related repairs. These requirements will allow independent repair shops to use a single diagnostic tool to access all of the information generated by the OBD II system for any manufacturer's vehicle.”

OBD III Have you heard anything recently about OBD III? Michael McCarthy of CARB shared some of the latest news about what's happening in this area.

“We paid a contractor to build up a couple of mock cars with remote transmitting systems and demonstrate that it was technically feasible to have a system that sends out a remote transmittal when the check engine light comes on,” said McCarthy. “A pretty basic contract since there are already systems like On-Star and LoJack.”

This prototype system was built by GM Hughes Electronics, and uses a roadside transmitter to interrogate vehicles as they pass by. The system is reportedly capable of retrieving information from eight lanes of bumper-to-bumper traffic whizzing by at speeds up to 100 mph!

“The concept is to stop requiring smog checks for every passing car and only test the failing cars. It would likely be a voluntary system - when you buy the car you could choose whether to go to smog check every two years or pay $xxx and never have to go to smog check,” said McCarthy. “You would, however, have to push a button on the dash once every three months that would send a signal that identifies your vehicle and the status of the check engine light. If you forgot to push the button you would probably get a letter in the mail telling you to press it or bring it in for inspection. If you pressed the button while the MIL was on, you would probably get a letter in the mail saying you have 60 days(?) to correct the problem and press the button again. If the MIL came on and you got it fixed before you pressed the button, you would never get any notice in the mail. There would not be a continuous signal identifying the location of the car or anything like that.”

RATE THIS ARTICLE What do you think of this article? Your input will help AutoInc. develop additional articles on this subject. Share your thoughts! Your name Your e-mail address

MOST ACCESSED ARTICLES Fuel Injection Service, Not Just Cleaning The Art of Extraction EGR Systems: Operation and Diagnosis Proactive Target Marketing:_Rethinking Your Business Strategy Engine Performance: HO2S Diagnostics MOST E-MAILED ARTICLES Developing Employee Potential How Critical Thinking Can Help Your Business How to Diagnose the Ford Glow Plug What to Look for When Shopping for the Right Shop Management Software Putting a Price Tag on Complaints

AutoInc. Web Site | ASA Web Site | NHTSA's Response: Caution, Disinterest or Funding | OBD II - 2000 and Beyond | It's Not Easy Being Green | Distance Education | Presidential Election 2000 | Guest Editorial | Tech to Tech | Tech Tips | Shop Profile | Net Worth | Stat Corner | Chairman's Message