What Actually Happens During An OBDII Emissions Inspection

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.

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