I was a bit surprised when I recently went in for an emissions inspection (I'm in Washington State) and they plugged into the connector under the dash. After starting and running at idle for a bit, the guy cheerfully reported I had "passed" and gave me a printed report and sent me on my way. None of the running at idle for 30 secs, then at 2500 RPM for 30 secs, as in the past. This test was on my 99 GM Truck, which has an OBD-II system, so I suspect older cars (like my 87, with the OBD-I system) still go through the old routine.

But, I found it fascinating that they would consider me good to go based only on readings from the ECM, rather than from the exhuast. From the report, it looks like it was checking the computer for signs of any engine codes, misfires, etc. It lists several systems that it supposedly "checked", such as Fuel System, Evaporative System, Catalyst, Oxygen Sensor and Heater, and EGR System.

My guess is that if you waltz in with a "fault" code set in your ECM, that you haven't bothered to deal with yet, you could fail the test. For example, I had a code set a while back, but it didn't effect runability. The check engine light went out after a few days; my mechanic suspected the gas cap might not have sealed properly. If that code had been set when I went in for the test, who knows what might have happened.

Just curious if other states are doing this kind of testing and if anyone knows what they are really looking for and what would cause you to fail.

 

They are looking for codes, just like you said. If they see any that deal with emissions problems they will fail you. I had my 96 tested this way almost a year ago...and at the time the car was running rich with long-tube headers and no cats. I was shaking my head when they gave me the thumbs up sign! They didn't even do a visual inspection of any kind, which I thought was a little odd.