Check engine light and emissions testing
In hope of helping other avoid having to go through what I just did, I will relate my experience over 2 months.
My check engine light was on, and like most, I believed that my vehicle would fail the emissions test because of it. It has been on every since I bought it over a decade ago. It always passes emissions with flying colors.
Anyway, since they passed a new law in 2015, I was under the impression that it would fail because the check engine light was on. I had done all the routine maintenance that you do anyway. Plugs, filters (including fuel filter) etc. I used Sea Foam in the vacuum lines, and BG 44K in the fuel. I waited until just before I had it tested to change the oil, in case any junk from those cleaners fell in the oil.
I then took it to a parts store because they will do a OBD II check. Well needless to say, they recommended this and that. (upon recommendations from 2 different auto parts store) after cleaning the mass flow air sensor, changing all three O2 sensors, smoke testing for vacuum leaks, and a bunch of other stuff, I took it to another shop.
They recommended changing out the "brain" at over $700. I declined, knowing that I had already spent more $$ than required for the "waiver" the emission place gives you if you spend enough $$.
I called the emission phone number to see what the procedure was to get a waiver. She asked what year my vehicle was, I told her it was a 1996. She said the law only applies to (now don't quote me here, because when I heard this I was SHOCKED) she said the law only applies to "something like" vehicles 2006 or 2008 or NEWER.
Here I was, for 2 months worrying about getting that damn check engine light to go off, changing parts, (have you ever done the "drive cycle" to get the check engine light to go off after replacing some part?) and everything else, only to find out it doesn't matter.
So I went to the emission testing center on the second to last day before I would be charged another $25 for being late getting plates (end of grace period) and had it tested. WITH THE CHECK ENGINE LIGHT BLARING AWAY. I wrote the check, handed it to the tech, and asked if we needed to call a supervisor? He said, "nope, it passed, and you are good to go."
Don't get me wrong, I want my vehicle to run as good as it can, and am still working on that check engine light. But don't expect an auto parts store, or a vehicle repair center to tell you this information. Their job is to sell you parts, or repair you vehicle, NOT to tell you that you don't need anything because your check engine light is on. Unethical maybe a little, but business is business?
Check engine light and emissions testing
I will try and avoid cluttering your thread with profanity but the whole "emissions test" thing here in Colorado is such a useless scam it isn't even funny.
In a nutshell, my truck was failed by some retard with a GED and a single digit IQ because my gas cap was "no good". Huh, so I didn't have any evap system codes (every vehicle sold in the United States since 1996 is required to monitor the fuel system integrity and will throw a code if my gas cap seal wasn't good) yet somehow this genius and his high tech vacuum pump machine say it's no bueno and fail me because I need a new cap.
Long story short, I have better things to do with my time so I replaced the damn cap and went back and they tested the new cap and passed me.
Two days later I now have a "gas cap loose" light on because the piece of shit aftermarket cap is junk. Being a little pissed off that day, I wasn't thinking clearly and tossed the original cap.
Looking forward to next time when they'll probably pass me even with the warning indicator that tells me my gas cap leaks being on because they'll likely test the cap and say it's good.
At least my vehicle is new enough that that they don't actually test my emissions when they do my emissions test. (Makes sense. They'll trust the on board diagnostics to monitor everything but won't trust it to monitor the freaking gas cap.) I hated having to watch some high school dropout with almost a year and a half of driving experience trying to run a vehicle on a dyno.