Noteworthy Vehicle Inspection Rules


There are two states in the country that come to mind when you talk about extraordinarily strict vehicle safety and emissions inspections, California and Massachusetts. I have never been to California, but I have had the pleasure of living in Massachusetts my entire life. This means that I have always had my cars failed tested for emissions, and a variety of other interesting laws. I have also had the distinct honor of being a Massachusetts state vehicle inspector, so I am quite familiar with the rules. Today, I wanted to cover a few things that may be helpful to you or possibly even entertaining to talk about.

Several years ago, cars getting inspections were run on the dyno to test the emissions coming out of a vehicle. A “sniffer” was shoved into the exhaust pipe, and with the car in motion, it sniffed out the carbon dioxide (CO2), carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx). Each vehicle had to be within certain limits that were built into the state’s computer program to pass the test. If not, you get the big black “R” stuck to your windshield, and have 60 days to fix it. If you had a car with non-disengageable AWD, you got the two-speed idle test (lucky rascal).  This meant that your car didn’t actually go onto the dyno. You just had to pass the emissions test with the engine at two different rpm’s. Those tests were significantly easier to pass because there wasn’t a load on the engine. For the inspector, this dyno testing was a gigantic hassle. The machine was often broken, most cars needed to be strapped down to the machine (time consuming & filthy), and brand new cars would randomly fail. The test was known to be inaccurate by everybody involved with it. After several years, the state recognized this headache and changed the test, for the good of everybody in my opinion.

The latest emissions inspection is far more intelligent, but not quite perfect in my mind. What it comes down to, is that 1996+ vehicles have OBDII (On Board Diagnostics Version 2), which means that the car’s computer knows when there is an emissions issue and stores it in its memory.  During the inspection, the inspector plugs the inspection machine into your car, checks your computer for emissions issues and passes or fails it based on what it finds.  Great right?  Less work for the guy doing the inspections, and likely a more “true” test of the vehicles exhaust cleanliness.  Cars built before 1995 are exempt from emissions tests because they don’t have OBDII, but……BUT…….. they do need to have the proper emissions devices in place.  That means that if the vehicle came with a catalytic converter, it better still have one.  It also means that if your car is billowing out a giant black cloud behind it as it idles, you fail.  It is up to the inspector to make the decision based on his / her expertise. If you fail for emissions, you get the big black “R” sticker on your windshield, announcing to the world that you are drivin’ dirty.  You then have 60 days to fix it before you become illegal.

Safety issues are safety issues. If you fail for safety, your car is probably not safe for the road, and you are putting everybody else in danger. You then get the scarlet letter on your windshield in the form of a big red “R”.  When you have this, you are no longer legally allowed to drive your vehicle on the road. You can be pulled over by the police, get a ticket, and have your car towed at your expense.  So, it is best to get it fixed ASAP.  My problem with the “safety” test is that it sometimes gets me when I least expect it. Being too low to the ground, to high off the ground, modified exhaust, having your license plate “frenched” into your tailgate, having any sharp edges, rusty rocker panels, non-working horn, a rock chip in your windshield, wheels that stick out further than your fenders, tinted windows, stickers on your windshield, and a plethora of other things are all failable offenses.  I often feel like many of these rules are written by people who have absolutely zero knowledge of cars.

Let’s have a look at some that are interesting or entertaining straight off the FAQ page.

  • “The windshield may only be tinted down to the AS-1 line, which is usually located in the uppermost (6) inches of the windshield.”  Good to know!
  • Neon (fluorescent) lights are illegal and are not approved for use in Massachusetts.” Your minitruckin’ dreams are over.
  • “By state law, Massachusetts license plates must be readable from 60 feet away. Any green or red passenger plate, which has lost its reflective coating or paint or has been damaged, must be replaced. You can also be cited by law enforcement for this violation.”  If your plate is frenched into your tailgate at a 45 degree angle, you will be hassled.

Now this is where it gets good. The website basically says that Massachusetts follows California Air Resources Board (C.A.R.B) rules, and then links to a list of approved repairs. I’m fairly confident that it is written by people that have never opened a hood before. Let’s see if we can make sense of it.

  • “Transmissions and transaxles changes alone are not legal. Transmissions and transaxles can only be changed along with their matching engine.”  Ummm, What?  I can’t replace my transmission without doing the engine at the same time!? ….uhh
  • “Electronic ignitions or electronic point replacement units for vehicles not originally equipped with these items require an Executive Order to be legal for street use.”  So I guess going from points to an electronic ignition is a bad idea now?
  • “Modifications that change a vehicle from fuel injection to carburetion or from carburetion to fuel injection also require an Executive Order to be legal.” …cringe.
  • “Headers for use on catalytic converter equipped vehicles require an Executive Order to be legal for street use.” Efficiency apparently does not equal cleaner emissions?
  • “Vehicles that were manufactured before emission control regulations took effect are called uncontrolled vehicles. Aftermarket parts regulations and anti-tampering laws do not apply to these vehicles.”  Thank goodness for SEMA.

Jeremy Nutt

Hi, I'm Jeremy.

22 thoughts to “Noteworthy Vehicle Inspection Rules”

  1. Time to get a NH PO Box. My car in high school had to be severely rigged to pass the idle tests. Luckily this was well before CELs and OBDII systems so with a little carb cleaner we were good to go!

  2. look forward to my inspection soon, gotta love mass. however, i do luck out on half the goodies listed – 87 was before obdII. However, the car WILL have it AND spew cleaner exhaust than it originally came with, not to mention better brakes and more stout suspension. Still, there’s the chance that because I don’t fit all the above criteria, I may get that wonderful scarlet letter. Here’s to crossing fingers and making buddies with the inspection dude.

  3. My ’53 crankcase vent dumps on the ground, gas tank vents to atmosphere, has two headlights, a tail light, windshield wiper, and a rear view mirror…

  4. Thank you for this posting, it has helped a lot.

    I have a question though. I live in Massachusetts and I am restoring a 91 Volkswagen Vanagon. Although I plan to keep the van street legal, mostly it will be a show car. One of the things I must do to the van to be show worthy is change the exhaust system. I have several options, but the one I am more interested in does not have a catalytic converter, but it does have a muffler. So the question is: showing up to the inspection shop with a pre-OBDII car that has a modified exhaust system without a catalytic converter will cause my van to fail inspection?

    Thank you so much for you advice.


    1. Hi David,
      Unfortunately, your VW needs a catalytic converter on it to pass inspection legally. The inspectors do look under the car to make sure it is visibly there, even though they don’t actually test to see that it is working. It could be empty for all they know, but it needs to be there.

      Also, FYI: If one of the inspectors gets caught for passing a vehicle that “shouldn’t” have passed, the inspector loses his/her driver’s license, and the inspector and the business gets fined. So, throw a high flow cat on there and make it easy on the inspectors. They are just trying to stay on this side of the law, and make sure the cars on the road are safe to drive. 😉

      Hop that helps! Got pics of your van?

    2. unfortunately, if your vehicle came with a cat originally, one has to be there to pass the visual (technically). while state law may not require it, federal law does and you can be fined for it too. however, modern cats are much better flowing than their old versions and power loss is usually only single digits.

  5. I agree that safety issues are safety issues, but after reading this and seeing that California is one of two states that have the most strict safety and emissions inspections, it makes me wonder if they might be overdoing it out here…

    1. I’ve seen the permanent brown smog cloud over LA personally so having cleaner emmissions out there is common sense, but in Mass where I live its pretty lame, of course the liberals here are uptight about pretty much everything fun…

  6. California can be very difficult as well when it comes to smog checks. Something simple like a gas cap can be difference between passing or failing.

  7. What if the car passes emissions with flying colors, and after it gets the yearly sticker, you change out the exhaust system to something…less restrictive 😉 but before the next inspection, you change it back to stock, just to get the new sticker, and once youre good for another year, you swap the exhaust system again?

  8. I think this OBD-II system is flawed. I know if the check engine light is on it automatically fails inspection. If it’s something that causes the emissions system to produce more pollutants than ok understandable, but my check engine light came on a one point for a bad cooling fan relay. I have an electronic fan as well as a manual crank fan so if the relay is bad the manual fan still cools the engine. I think it’s ridiculous that in order to pass inspection I have to replace the cooling fan relay just to get the engine light off. The cooling fan relay will not mess with the emissions, so why should it fail for that? I think it should be up to the inspector depending on the codes for the MIL to pass or fail the car, not just an automatic failure. I know that’s an argument to have with the state, just putting my 2 cents in as to how the rules don’t make sense.

    1. Hi Jen,
      I can most certainly relate, as I too have failed for (and been pulled over for…) some ridiculous things over the years (Dirty license plate anyone?). Anyway, like you, I think having a bad fan relay that turns on a check-engine light is quite nutty, but I think I know why they designed the car to do that (even though I don’t agree with it).
      When an engine runs hotter than intended, NOX gas (nitrogen oxides) is created and dumped out the tail pipe in the exhaust. That is one of the 5 big emissions that the state/gov is trying to prevent, because when combined with sunlight, it is a major contributor to smog. My guess is that when the engineers designed your vehicle’s computer program, they assumed “well, if the electric fan isn’t working, then the engine MIGHT run hot, and create NOX emissions ::GASP:: – so let’s turn the check engine light on for that.” In reality, that may not be the case because as you said, your vehicle has an engine driven fan, which likely does the job of cooling the engine just fine (They worked great for about 80 years of car evolution). Your electric fan is likely only used when running the A/C or on really hot days in traffic.
      You would think that the car maker would design a computer system to measure engine temperature / exhaust temperature / actual emissions instead of setting a CEL for a fan relay, but I guess we just weren’t there yet when your car was built. Luckily, cars keep getting smarter. So although the engine driven fans that worked terrific for 80 years will be a thing of the past, the computers that run the engines are beginning to understand the difference between a bad fan relay, and a REAL emissions problem.
      That being said, if you haven’t fixed your car yet, there are aftermarket relay kits out there for problems like these. Relays almost almost work the same exact way, and are very easy to wire in if you know which wires are which on the vehicle side. You could also hit up the local junkyard and probably get the relay that you need for $5. Good luck, and let me know if you need any over-the-internet guidance with it. I’m happy to help!

  9. I drive a 2001 PT Cruise which has a 2-speed radiator fan. The computer is misreading its connection to the low-speed fan which means it won’t turn on. The high-speed works fine. The only solution I am aware of is to buy a new computer, $$$, which I am hesitant to do -yet. I’ve had the high speed fan wired to turn on when I start the car. This has worked fine for nearly a year – but the check engine light stays on because the computer can’t connect to the low speed. I think I should be able to pass inspection regardless of the low speed fan not working – but the damn check engine is on so I’m having a hard time getting a garage to inspect my car. Does anyone know if I need the fan to run to pass inspection? I don’t believe there is an emissions problem. The car only has 107K – plenty of life left. I’m in the Cape Ann area.

  10. I have a 1995 G M C Jimmy 4×4 it has a cat but i need to have it removed and I have been told by different shops that i do not need to put a new cat on and i can go with a just a stright pike where the cat is i know all i have to go through is the safety but tring to find a correct answer on the cat part

  11. In Massachusetts, is replacing bad catalytic converter to non CARB converter ilegal?
    OE catalytic converter is too pricy. Some after market converters look good enough.

  12. replacing a cat is pretty much illegal per federal regulation. basically they say that even if the cat fails your are not authorized to replace it. something to that effect. check federal cat regulations on google.

  13. so on another note.. is there a recommended place in NH where I can get my car inspected. I have test pipes. But I guess if the only thing they are looking for is a CEL i can turn that off. Will this suffice for inspection purposes? thanks.

  14. If I fixed everything the inspector told me to, can they find something else and fail me for that? I am in Massachusetts.

    1. Hi Kristina,
      When the first inspection was done, they should have “approved” some things and “failed” others (check the print out that they gave you). When you re-do your inspection within the time frame allotted (60 days I believe), and go back to the same inspection station, the state inspection computer will only care about inspecting the items that previously failed. It won’t do another emissions test for example, unless that is what you previously failed for. That being said, if you are beyond the allotted time limit, or your car is now clearly dangerous to the inspector (bald tires, missing headlights, etc), they have every right to fail you for anything that doesn’t pass. If the inspector does pass a car that is unsafe, and gets caught by the police/state – they get a massive fine, and they lose their drivers license. So most inspectors don’t want to risk that. Hopefully that answers your question! 🙂

  15. So what are the rules about rust? I was going to fill in some holes on the bottoms of the rockers with spray foam insulation. Just trying to help my friend get through one more year

Leave a Reply

Your email address will not be published. Required fields are marked *