by Henry Cipolla
I have seen many people talk about OBD-II emissions tests on various web forums. Often with a puzzled: “I failed readiness!” or “Do I have to do an OBD-II test on my 1994 vehicle?” Since OBD-II has replaced or will replace sniffer tests for 96 and newer vehicles in most states, I thought I’d dump some introductory information about OBD-II emissions tests for people. I don’t get into the details about OBD-II, the various protocols, or how to tune an OBD-II vehicle here. Only what to expect in the emissions process.
First, some really quick background: California required emissions control systems (Catalytic converters) on cars sold in California starting the 1966 model year. This was adopted across the US in 1968, and eventually became the Clean Air Act of 1970 which required emissions standards that were hard for manufacturers to meet. Ultimately, car makers found that switching to electronically controlled engine management allowed them to meet these demands. These electronics became more sophisticated and more standardized as time went on, and now we have a standard protocol (OBD-II) that all these computers adhere to.
Today: Many States, California, Massachusetts, New York, Illinois, Washington, New Hampshire, and on and on have mandatory emissions inspections in some or all counties. Typically this is used as part of the car registration and renewal process. Up until 2000, this just meant popping the car on a dyno, sticking a sniffer in the tailpipe and measuring what percentage of the air coming out of the vehicle is clean. However, in 2000 the EPA started pushing an “OBD-II emissions test” and many states adopted it, or are in the process of adopting it.
An OBD-II test consists of the emissions computer plugging into the OBD-ii port on the car (usually under the dash or hidden behind the cigarette lighter) and asking the car’s computer whether the emissions equipment on the vehicle is working within the required efficiency limits. This is advantageous over the sniffer because its much faster, more consistent (in theory) and harder for those of us that like fast cars to just jury rig a huge catalytic converter the morning before inspection in order to pass with flying colors in our fire-spitting vicious mobiles
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