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OBD-II Vs. Emissions TestingPosted 5/11/2005
By Alexis Gross
Vehicle onboard diagnostics (OBD) has evolved over the last 20 years. What began as a small set of manufacturer-specific tests and communication protocols has evolved into a complex, comprehensive diagnostic system able to detect literally hundreds of failures that could cause driveability concerns or emission increases. This rapid evolution has been driven by California's technology-forcing OBD-II regulations as well as the need for manufacturers to provide comprehensive diagnostics to allow technicians to service the complex engine and transmission controls on today's vehicles. As technology improves, states are relying on onboard diagnostics for inspection and maintenance (I/M) programs in place of tailpipe emission tests.
"If the state is in noncompliance with ambient air quality standards, one of the only mandatory aspects of that compliance is mandatory inspection and maintenance programs," said Mike McCarthy, manager of advanced engineering for the mobile source control division for the California Air Resources Board (CARB). "The EPA also says I/M has to include using the OBD-II system. The other thing that drives states with regard to I/M is how much emission credit the EPA says they're going to get from running various emissions programs."
One thing that model says is that an OBD-only program provides at least as much benefit to air quality as a tailpipe test. States are always looking for the most cost-effective program that gives them the most emissions bang for their buck, and this, along with when the state contract with the network contractor is up, are the two great determiners of how soon many states will be switching to OBD-only testing programs.
Robert L. Redding, ASA's legislative representative in Washington, D.C., said, "Clearly, regulators are encouraging OBD-II testing. We need to spend more of our resources on expanding programs in areas with air quality issues or that contribute to communities in nonattainment. The trends for testing are evident; we should support these programs if possible, and work with those administering the programs. Expansion of the programs is the key to the repairer's I/M future."
One of the benefits to OBD testing is that its equipment is dramatically less expensive than that needed for tailpipe testing. For states just beginning their I/M programs, it makes sense to begin with an exclusively OBD-II program. A full tailpipe testing workstation costs in the area of $40,000, whereas OBD-II testing requires little more than a scan tool and a modem. Some states don't even need a printer for a window sticker, since the inspection information is stored on the state motor vehicle database and tied to the vehicle registration.
McCarthy believes OBD-II testing alone can give as many or more benefits than tailpipe testing. For one thing, the system is constantly operating, monitoring any problems the vehicle experiences, thus it catches trouble long before a tailpipe test could detect it.
For another thing, he said, as manufacturers continue to improve their vehicles, sources other than the tailpipe are becoming a larger culprit in emissions failures, like the evaporation system.
"OBD does a leak check on the evap system. Most state's tailpipe tests at most have a gas cap test. OBD tests the whole evap system," McCarthy said. "As cars have lower and lower tailpipe emissions, evap emissions play a larger and larger role. Hydrocarbon emissions are greater from the evap system than from the tailpipe. Most tailpipe tests are blind to evap failures, so there alone you will pick up benefits that tailpipe testing doesn't have any chance of catching."
One question receiving a lot of study is whether OBD-II testing is as - or more - effective than tailpipe testing.
"It really is a state-by-state issue," said Chuck Rhodes, inspection and maintenance district supervisor for the Wisconsin Department of Transportation. "Wisconsin state law requires emissions testing of '68 and newer vehicles. Some states are hitting 86 percent of the fleet that is '96 and newer. We're 55 percent '96 and newer."
Other states, such as California, have a much older fleet of cars on their roads, and need as much emissions credit from the EPA as they can get. State law requires that all cars, even those that are OBD-II capable, undergo tailpipe testing.
Rusty Savignac, co-owner of Paxton Garage in Paxton, Mass., was involved in the development of the Massachusetts emissions test. He said about 6 percent to 10 percent of vehicles fail the OBD-II inspection, much higher than the near 3 percent that fail the tailpipe test.
"It's a controversial subject," he said. "It depends on the type of tailpipe test being conducted. Every state is different and they vary in accuracy and comprehensiveness. Our experience in Massachusetts was that it was a rare occasion not to fail both tests. Most cars that failed the OBD-II test failed the tailpipe test.
"That has a lot to do with the ability of the redundant systems in the car that keep emissions in control. Secondly, our tailpipe testing limits are somewhere near six times the federal test procedure (FTP) limits for the car. In theory, the malfunction indicator light (MIL) is supposed to come on when the potential exists for emissions to exceed 1.5 times the FTP."
Joe Torchiana is concerned that this formula will not continue to work in high-mileage vehicles. Torchiana owns One Stop Tire & Auto Service Inc. in West Chester, Pa., and is current chairman of ASA's Mechanical Division Operations Committee's Emissions Testing Subcommittee.
McCarthy sees things differently.
"We are rapidly approaching a point where our (tailpipe testing) equipment will not be able to determine clean and dirty cars because FTP standards are for lower and lower emissions levels," said McCarthy. "You can use this equipment to pick out the dirtiest of the dirty, whereas in the past it tried to catch cars at moderate levels. OBD equipment is correlated to work for the standards a specific car is built to, versus a tailpipe test that is supposed to fit every car out there. If tailpipe testing is going to serve a role, it's going to serve a different role than it does today."
What is the future, then, of OBD-II and emissions testing? Technology exists today that would allow inspections to take place without any contact with an inspection station or repair facility. FM or cellular transmitters can relay OBD information to a state information database or the nearest manufacturer dealership. Systems like OnStar are capable of performing emissions tests. Self-service OBD-II kiosks, like ATM machines, have been suggested. Motorists could even perform their own emissions inspection at home and send their results in to their state program.
As testing becomes more and more remote, however, the maintenance part of inspection and maintenance programs could become even more difficult to enforce than it already is, said Torchiana. He worries that the emphasis placed on training inspectors to administer the test rather than training technicians to repair the problems is a great shortcoming of emissions testing programs.
"Emissions testing programs are a mandate for the consumer to fix the car and the technician to make money if he fixes it properly," he said. "I'm not aware of any other industry where the federal government makes a customer pay money to take care of their product and enforces maintenance and repair of that product, and we (technicians) are the ones that fumble and don't fix the cars."
Most states that have I/M programs require emissions inspectors to undergo training and certification in the inspection process. In most places, that training must be renewed every two years. In addition, some states require that emissions-related repairs be performed by a licensed technician.
In California, said McCarthy, "not as much time is spent on diagnosing and understanding the trouble codes that come up during inspection. It's actually illegal for inspectors at inspection-only stations to offer advice or repairs. The focus of training is mainly on the rules and procedures to run the test. Most data is sent electronically and is not subject to interpretation."
The pass/fail nature of emissions testing is partly to blame, said Torchiana.
"There's no marginal failure, so there's no impetus for the technician to plug into the car and find out if it's good, bad or indifferent," he said. "It's pass/fail instead of a grade point. I think there's information available in the data stream to determine performance better than just a pass/fail."
As in the rest of auto repair and service, ongoing training is the key to a good repair and a profitable shop, said Rhodes.
"I look at OBD-II as a tool, like the computer on my desk," he said. "Its job is engine control and it does it electronically rather than mechanically. It also can detect emission components and tell you when they're failing. You still have to go to school and train, or OBD-II will just be another wrench in the box that you don't know how to use."
And that wrench will continue to sit in that box and grow in size and importance, said Rhodes.
"If you throw emissions out of the discussion, onboard diagnostics is the way cars are built," he said. "The industry is not going back. In the type of cars that are built now, the engines last longer and OBD-II lets them last longer because they're running more efficiently.
"OBD-II is an integrated system that can improve how a vehicle operates. It started as emission control, but like any computer, you can expand the capability of what it does. OBD-II can make repairs as it goes down road, like minor corrections in timing. When the MIL actually lights up, that means the car tried to fix itself and identified something it can't do, and it's asking you to repair it."
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