BUT IT PASSED THE LAST TIME......
And that was 2 years and some 30, 000 miles back. Your "Check Engine" light wasn't on full blast, the tune up had just been done, the radiator fan was keeping things cool, the tires were properly inflated, you could afford to run it on premium gas, you just happened to be tested on a cold, damp day but this time your vehicle failed..... What's wrong, it passed fine last time?
The State of California,in an effort to get more and more vehicles to fail smog check, makes the test harder to pass and either lowers the maximum allowable emission standards or increases the number of required inspection steps and the very next day many "marginal" vehicles (pass one day then fail the next because the readings are very near the fail point) fail, that would have passed the day before. Just your lucky day. Why, you ask, would they play this trick on us? Hmmm....let's see now, the more vehicles that fail the inspection means more vehicles get repaired, which means cleaner air for us to breathe, when those repairs are done. Well, if the state makes it harder to pass, it's only fair that they understand the financial burden that will fall on us when our failure occurs. Who can afford those expensive repairs? Realizing this was the main problem, the "Consumer Financial Assistance Program" was born, so all would be winners, you, the state, and the feds.
Passing the last time tested is no absolute guarantee that a vacumn hose didn't misplace itself, or any number of parts required to pass the test remain intact some two years later. I know, your regular mechanic said " just ignore that stupid little light" on the dash. Now the smog testing machine hooks up directly to the vehicle's computer detecting the light and automatically failing the vehicle. Of course if you are being sent to a "TEST ONLY CENTER " station for your inspection, the state may very well fix that problem for you saving you many hundreds of U.S. dollars. Remember, there are many ways to fail, but only one way to pass.
If you know someone who knows their way around underneath the hood, before you go for the smog check, ask them to pop the hood and have a look around to see if all is in order. If no one is availiable to help, I'm here and willing to do so. Might save you some grief later. And perhaps a grey hair or two.