[KingMachiavelli]

In my state they will just do engine light & ECU test for new cars. On older cars (>=10 years) when they do the IM240 test on a dynamo but if you look at the emissions limits they are all 100x what a normal car produces. Here's the GPM values (reading/limit) from my last test on a 2011 Honda Pilot:

Hydrocarbons 0.023/1.2 (1:50) CO 0.3/15 (1:50) CO2 502/NA (guess this one has no limit?) NOx 0.081/2 (1:25)

Maybe some states apply newer, stricter limits to older cars retroactively but in my experience as long as a car is operating normally it is impossible to fail emissions. I wouldn't be surprised if the ECU threw a code before the dynamo test caught something. IMO the most practical check they actually do is the presence of a functioning gas cap.

[Scoundreller]

> IMO the most practical check they actually do is the presence of a functioning gas cap.

Even that throws a code these days. 14y.o. BMW has a pump that pressurizes the fuel system to check for leaks and it’s usually the pump that breaks and throws a code.

17y.o. Corolla threw a fuel system code but it was the gas cap.

Only thing is that this pressurization check system only runs when the weather is warm enough, so resetting a code usually lets you pass e-testing as “Not Ready” because months can go by. Maybe there’s differences in summer/winter e-testing criteria.

[rootusrootus]

I don't know if it happens this way any more, but my last Subaru would do the pressurization test about 30 minutes after the car was turned off. Kinda weirded me out the first time I went into the garage and heard what sounded like something in the rear of the car inflating. Turns out that is exactly what it was doing.

[frosted-flakes]

Ford vehicles also do this.