This is a B EM W being tested on the OIS.

I’ve talked a lot about different aspects of the smog check program in California, but I’ve never gone over exactly what an inspector does during a smog test. So let’s go over that today.

First off let’s talk about what cars get smogged in California. In California, we smog both gasoline and diesel vehicles. Any gasoline vehicle 1976 or newer, and with a GVWR of 14,000 pounds or less get smogged. Only diesel-powered vehicles 1996 and newer with a GVWR of 14,000 or less are smogged. We also smog cars powered by propane, and natural gas (CNG, LNG, and LPG). Anything that pertains to “Gasoline” also pertains to natural gas cars. Other than, I’ve never even seen a propane or natural gas powered car. And starting with the new rules which came out around 2012, we do smog hybrids now. And I should note that when you buy a brand new gasoline car it doesn’t require a smog for six years. Diesels aren’t exempt.

And I think I should also briefly discuss what one has to do to become a Smog Inspector in California. Or rather I’ll tell you how I got mine and you can refer to the document below to see the full list of options. I was able to test for my Inspectors License by taking three BAR courses at my local community college while I was finishing my AA in Liberal Arts and also going through the school’s automotive program. They’re simple courses if you know what you’re doing, and the test was really easy.

But California also has a Smog Repair Technician license. You see, in California only LICENSED Smog Repair Shops may fix any vehicle that has failed a smog inspection. And to be a licensed Smog repair shop you must employ a licensed Smog Repair Technician. One requirement o test for that license is that you must have ASEs in A6: Electrical Systems, A8: Engine Performance, and L1: Advanced Diagnostics. That’s how I got my license. You can also qualify based on educational experience.


So now back to the actual smog check. Now you know what vehicles we have to test, and how to become an inspector and repair technician.

So for cars 2000 and newer, with a GVWR of 14,000 pounds or less, I use a machine we call the OIS. This test does not require a tailpipe check. We do an OBD check where the state computer thingy checks some parameters, checks for current codes, and checks the emission component monitors (more on that in a minute). After the OBD check, we do a visual check.

This isn’t my shop, but the machine in the middle is the BAR 97 machine.


For cars 1999 and older, or over 14,000 pounds I use a machine called the BAR 97. This one adds in a tailpipe check for all of the cars. And when the car doesn’t have OBDII then we add in up to three functional checks that the Inspector performs.

So let’s break down each portion of the tests:

OBD check: the test is only checking for current codes that have commanded the MIL on. If there are pending codes the car WILL pass this portion of the test. It’s also checking to make sure that certain emission component monitors are set as “ready.” This is the biggest point of failure. Without getting too deep into how OBDII works, the way the MIL actually turns on is after the computer runs self-tests on the major emission components. There’s the Comprehensive monitor, miss-fire, fuel system, catalytic converter, O2 sensor, heated O2 sensor, and if the car is equipped it will have EGR and then AIR. The first three are continuous monitors, and what means, basically, is if there is ever a fault within those “systems” the light will turn on right away. The rest all require a specific type of driving, called a drive cycle, in order to properly test the components and to set the monitor. For the sake of simplicity let’s say the cat monitor only runs if you drive the car between 40 and 60 mph for 15 minutes. As soon as you do that, the monitor will show “complete” and if there is no fault with the cat, there’s no code. If there was a problem you usually get a pending code. P0420 and P0430 are usually two trip codes, meaning you need to complete the drive cycle twice and have the component fail the test before it turns on the light.


So for gasoline cars 2000 and newer, the state only allows the EVAP monitor to be incomplete in order to pass the OBD portion of the test. They did this because the EVAP monitor is a bitch to run, so the state doesn’t require it. For diesel vehicles 1998 - 2006 there can’t be any incomplete monitors; I don’t why it’s 1998 and not 1996. And 2007 on they allow two incomplete monitors.

Now let’s move on to the tailpipe test for cars 1999 and older. If the car being tested does not have any restrictions, like full-time 4WD, or AWD, or non-disengageable traction control, we do what’s called an ASM test. ASM stands for Acceleration Simulation Mode. The vehicle is tested with a simulated load on the dyno and it’s tested at two speeds: 15 mph and 25 mph. For automatic cars, we’re instructed to put in Drive and that’s it. For manual cars, we’re supposed to keep the car in second gear only. The way the state tells whether it’s in the right gear or not is based off rpm. They allow a range of 1500-3000 for engines under three litres. Anything larger than that and the range is 1200-2500. If you intentionally test too many cars in the wrong gear bad things can happen, but that’s a story for another post. The test is checking the car to make the gas levels for HC, CO, and NOx are within range.

For vehicles that can’t be tested on the dyno, though, we do a test called a TSI, or two speed idle. We test the car for 30 seconds first at 2500 rpm, and then at idle for another 30 seconds. And when a car requires a TSI and it’s a 95 or older, and it has EGR, then we’re supposed to manually check that the EGR works. But we can only do this on vacuum controlled systems. I just hook up a vacuum hand pump to the valve and open it and the car should die. That’s how we “test” for NOx because NOx isn’t measured with the TSI.


Now let’s move onto to functional testing for gas cars 95 and older. Since these cars don’t have OBDII, we have to check, where applicable, the ignition timing, the EVAP system, the gas cap, and the EGR (see above paragraph).

Timing is pretty simple. Most cars are adjustable. I figure out that via the emission control label. That label tells me what year it is, what engine it has, whether it’s a California or Federal car, what emission components it has, and for 95 and older, whether timing is adjustable. And if it is, it tells me how to check timing.


So whenever timing is adjustable, the ignition timing must be within three degrees of that spec, unless the label says otherwise. Honda is the only one I can think of that has a deviation, and it’s plus or minus 2 degrees. Besides the timing deviation, the engine speed must be within a 100 RPM of what’s specified. I can find the engine speed either on the label or in Motor manual we are all required to have.

This is the EVAP tester.

Next, we move onto the EVAP functional test or LPFET. To do this we use a separate piece of equipment that has a hose which, with an adapter, goes onto the fuel filler neck. Then we pinch off the carbon canister so that the LPFET pressurizes the gas tank and associated tubing and checks for leaks. The system passes if it has a leak smaller than .040”. If the carbon canister isn’t accessible, or it uses plastic tubing, we don’t test it. And on bigger trucks with two tanks, we don’t test that at all. We also do a fuel cap pressure test which is attached to the BAR 97 machine.


And that’s it for functional tests on gasoline cars 95 and older.

Now onto the big one: VISUAL. This is the portion of the test where the technician is supposed to look at all the major emission components (aka the engine and everything attached) and check for anything broken, missing, or modified. This is the portion of the test where I would fail a car that doesn’t have a CARB legal cat. The visual portion really is the most important bit because it’s the part that is most easily faked. All a technician has to do to pass a car with an illegal part is just enter “PASS” into the OIS or BAR 97 machine. And this is also why I am usually the bad guy: I pay attention and I always check things.


But let’s go over the Visual in a little more detail. The picture attached is of a checklist that is in the 2017 Smog Check Manual. This list guides the technician on whether a particular part might need an EO number. As many of you might know by now from reading my past posts, an EO, or Executive Order, is CARBs official okey dokey on any particular part. For any system CARB deems to need an EO number for a modification, the manufacturer needs to prove the modification does not negatively affect emissions. The above picture also shows you a little more detail about what is considered an “emission component.” And this is the first update to the Smog Check Manual since 2013, and this list contains a lot of new things which is great because I’ve failed cars for things that are apparently now legal. If you scroll down into “Other” you see “oil separator/filter crankcase gas filter.” Well, before this manual update, I was under the impression that any re-routing of the PCV system in any way without an EO number was illegal. I thought it was dumb since I know that oil separators are a good thing and they keep the gasses inside the engine and they’re actually reducing pollutants and waste by keeping oil out of the combustion chamber. But I had been instructed to fail a car with a modified PCV system. I am ecstatic to see that I can now pass cars with catch cans and such.

Another area where the state has changed things is intercoolers. I was always under the impression they were illegal without an EO number, and I failed a car a few months ago. Again, I thought it was stupid, but I was doing what I believed the state required. So now California residents can cut their bumper up and stick a big ass intercooler up front.


Exhaust systems: Contrary to even some manufacturers belief, any exhaust modification after the catalytic converters, aka “cat backs” have always been legal. They may violate other sections of the California vehicle code, such as § 27150 (a) Every motor vehicle subject to registration shall be equipped with an adequate muffler in constant operation and properly maintained to prevent any excessive or unusual noise, and no muffler or exhaust system shall be equipped with a cutout, bypass, or similar device. But as far as smogging goes, the state has never cared what you did after the required after-treatment component. And I actually failed a car today that had oversized pipes before the two converters. And lo and behold he’s had it like that for 15 years. But apparently, I was the first one to actually stick my head under the car and see the modified exhaust.

Another surprising addition was water injection. Cool bro! And I’m also glad to see additional fuel filters are allowed for diesels because I wanted to add in another filter for my TDI when I get around to replacing the HPFP.

But now a little bit of why I always err on the side of caution, and why I take my job so seriously. I am licensed by the State of California through the Bureau of Automotive Repair. My license is governed under several sections of the California Health and Safety Code, and also the California Business and Professions Code. The state can and does use its authority under relevant government codes to prosecute and or fine technicians who do not do their job correctly. Ultimately a technician can be charged with a felony in addition to having their license revoked, and being slapped with a big fine. But that really only seems to happen when the technician is running an illegal operation to systematically pass illegal cars. In the case of normal technicians, though, the BAR sends out undercover cars which have been prepared to fail the visual inspection, but only if the technician notices. They do this not to trick people, but to just make sure technicians performing smog inspections are doing them correctly. When a technician is caught passing an undercover they are usually just issued a slap on the wrist and sent to remedial training. When it happens again they’re usually hit with a fine between $1,000 and $5,000. Plus the shop is usually hit with a $5,000 fine. As the technician keeps getting cause the fines go up. It’s, for this reason, I am always very thorough when performing smog inspections. It’s why I check every single aftermarket catalytic converter. It’s why I always do an underhood inspection with an actual flashlight. And it’s why I err on the side of caution. The state also has Smog Referees that consumers can take their car to when they feel their car should have passed. Or technicians can send the car there. I will occasionally send people there, but most of them are so pissed off their car failed I doubt they listen to me and probably go to another shop.


But there you have it. I think I covered everything. The OBD portion, the functional checks on older cars, and the oh so important visual inspection. Hopefully, this post was informative and illuminating. However, this post is in no way meant to argue the debates of the smog check program in California, EO numbers, CARB, or whether you can mod your own damn car however you damn well, please. This is meant as an informative post for everyone, whether they live in California. Thanks for reading.