Guide on how to pass Smog

2sporty · 09-16-2023, 04:16 PM

I am writing this to help everyone because I believe the smog check racket, especially in CA, is absolutely ridiculous.

I have gathered this information by reading pages and pages of eye bleeding bullshit and a few precious tidbits of valuable information. The rest I had to discover by myself from trial and error. You can find and derive most of this information by searching, but it's scattered everywhere in fragments.

To pass CA Smog check, which is the most strict smog check in the country, there are two main conditions:

1) Your CAL ID/CVNs have to match (if you've tuned the car with software, they do not match)

2) All of your smog check monitors have to pass in CA except for the EVAP monitor.

1)
What is CAL ID/CVN? It's a checksum for your DME and TCU. If you have made any modifications, the checksum will not match because, by tuning, you have modified bits in the software.

After reading many posts on CAL ID/CVN. I initially thought our cars had one CAL ID and one CVN that has to match. Guess what? In our cars there are TWO SETS of CAL ID/CVNs. Why are there two sets? Because one corresponds to the DME and one is the TCU (transmission control unit). If you modified your car with an engine tune, it modifies the DME. If you did a transmission tune (ie: XHP or bootmod transmission flash), it modifies the TCU.

Now here's the catch. Some tools don't even make a backup for you, so you cannot get the CAL ID/CVNs to match by flashing back to stock using their tool! Bootmod will get CAL ID/CVN to match FOR THE DME ONLY if you flash back to stock and re-lock the DME. If you flashed the bootmod transmission flash, as far as I know, you're out of luck. The TCU CAL ID/CVN will not match. You will need to flash a stock TCU. I had kubax86 do this remotely and I highly recommend him.

You need an OBD tool with mode $9 or ISTA in order to see the CAL ID/CVN. Some crappy OBD tools only show one set for some reason. The Innova 5210 is the cheapest tool I could find that reads all of them. Both sets of CAL ID/CVN must match. The alphanumeric strings have to literally match.

2)
After you have flashed back to stock, you need to check your "monitors".

Smog check monitors are the checks that your car performs in order to verify that it is emissions compliant. When you do something like reset the DME to stock, there will be about 5 monitors that will show up as NOT PASSED. This does not mean fail, it means that the test needs to be run on them. How do you run the test to make them pass? Do the bmw drive cycle as shown in the image I have attached. I do this with the "Car Scanner" app on the iPhone with the "emission tests" part open. You can see it live as the monitors turn green, into "PASSED" as you do the drive cycle. In California at least, every one needs to be "PASSED" except for the EVAP monitor before you take it in for a smog check.

hardware modifications:
If you have a downpipe with no catalytic converter (and no way to bypass this check), you will not pass some monitors.

visual check:
If you have midpipes, which eliminate the secondary cats, you will pass, unless they visually check that the secondary cats are gone. Most stations won't check unless they are super anal or have an incentive to fail you and make you come back and pay again. If your car looks stock, there is generally less of a chance they will check. Not everyone is going to bend their ass down and put their head on the ground on every single car to check. They'll trust the ECU most of the time unless your car (or perhaps you) "looks suspicious". If you drive a car that you can pull up to your relatives and co-workers with while still being able to look them in the eyes, you'll likely pass visual unless the checker is a total asshat.

greysea · 09-16-2023, 07:25 PM

Thank you for posting this. I am in northern CA and just recently went through hell selling my lexus is350 and having a wrong carb sticker that was for a 2014 and not my year which was 2015.

I am very hesitant on doing any tuning or exhaust mods because it is a real headache. Especially if you get sent to the state ref.

So far I have only done cosmetic mods. But I really want to do a bm3 stage 1 tune and get AA EL midpipes or single and call it a day.

Doing the stage 1 and midpipes might be worth this headache every two years. I really want that sound plus that hp/tq increase. It is awesome (on paper and youtube vids lol)

Hxngs · 09-17-2023, 07:50 PM

since I have a manual. I only need to worry about the DME matching?

Wanted_M · 09-17-2023, 08:48 PM

Or try Weistec tune stage 1 since its CARB approved. I don't know anyone using their tune but as far as I know, it's the only M3/4 CARB approved tune.

FaRKle! · 09-18-2023, 11:55 AM

There's another option for #1, find a tuner that knows how to make the CALID/CVNs match the stock values even with their tune

. You won't find this with anybody using a 3rd party platform to tune though (like BM3).

Tangent · 09-18-2023, 01:10 PM

Quote:

Originally Posted by greysea

Thank you for posting this. I am in northern CA and just recently went through hell selling my lexus is350 and having a wrong carb sticker that was for a 2014 and not my year which was 2015.

...

That triggered a bad CA smog check flashback for me. Many years ago I had an 89 Camaro and it had a fairly minor accident. Everything got repaired but apparently Chevy no longer made the CARB stickers for under the hood that included details like the engine timing needing to be set to 0*. The problem started when I discovered every CA smog shop manual showed that the timing should be 3 or 4* BTDC as was more common on Chevy V8s. So I was left with the choice of failing because of the wrong setting, or failing because it wouldn't pass the sniffer with the settings they thought it should have. Gotta love this state...

2sporty · 09-18-2023, 07:20 PM

Quote:

Originally Posted by Wanted_M

Or try Weistec tune stage 1 since its CARB approved. I don't know anyone using their tune but as far as I know, it's the only M3/4 CARB approved tune.

I am inclined to not use their tune due to them bowing to California and paying the fees to get CARB approved. I prefer spitting in the face of the insane and authoritarian California government that enjoys putting our tax dollars to waste by using the aforementioned smog circumvention tactics.

greysea · 09-18-2023, 08:03 PM

Quote:

Originally Posted by 2sporty

I am inclined to not use their tune due to them bowing to California and paying the fees to get CARB approved. I prefer spitting in the face of the insane and authoritarian California government that enjoys putting our tax dollars to waste by using the aforementioned smog circumvention tactics.

Not to mention the 1199 price tag they want.

Think I would rather cruise the forum selling their BM3 license cheap and snag that.

Then do your route of relocking DME and grabbing a smog tool off amazon to make sure those numbers match up and all green checks besides the evap.

Giving me confidence in doing it. Hell I am even looking at doing a midpipe.

2sporty · 09-19-2023, 03:24 PM

Quote:

Originally Posted by greysea

Not to mention the 1199 price tag they want.

Think I would rather cruise the forum selling their BM3 license cheap and snag that.

Then do your route of relocking DME and grabbing a smog tool off amazon to make sure those numbers match up and all green checks besides the evap.

Giving me confidence in doing it. Hell I am even looking at doing a midpipe.

Bootmod is great if you want only the DME flash. I asked their customer service about how to get the CAL ID/CVN to match for the transmission flash and they didn't respond. I am surprised they overlooked this, considering a great deal of their customers are from California.

Hotflare · 09-26-2023, 09:26 PM

Thx For this bro

bholler · 09-26-2023, 09:58 PM

Thank you for all this great information and curated nicely. This jives with my research and held in my head.

Bummer to hear about the Transmission CAL ID CVN. Never heard about that one.

Not looking for to have to deal with that in 2025. Hopefully there is fix by then.

WeekendWarriorz · 09-27-2023, 12:30 AM

Quote:

Originally Posted by 2sporty

Bootmod is great if you want only the DME flash. I asked their customer service about how to get the CAL ID/CVN to match for the transmission flash and they didn't respond. I am surprised they overlooked this, considering a great deal of their customers are from California.

most people here pay to play/go back to stock for smog or commonly find someone who can smog the vehicle which is modified.

Changtownriot · 10-16-2023, 02:32 PM

I’ve been getting ready to smog my car and did the drive cycle Friday night. Got every monitor to be ready and thought I was good. I was going to take it this Monday morning for the smog check and I figured I should check the monitors again before I go. For some reason all the monitors that were ready on Friday were no longer ready. No idea what would cause this since the car battery didn’t die or anything? Does anyone have an idea of why this would happen? The only thing I could think of is I have a exhaust flap controller that plugs in through the obd port, maybe that caused the ecu to drop voltage and reset? Sounds crazy to me but I’m stumped on what’s going on.

jwagman1 · 11-07-2023, 02:42 PM

Thanks for this!

Cant tell you how many people fight me when i say you gotta remove tune and relock dme. In other states you may get away with it, but no in California!

I am going back to stock this weekend to get my CA Smog. Sucks gotta do it every 2 years from now on, but at least i can do the work myself so its not costly!

greysea · 11-07-2023, 07:08 PM

Quote:

Originally Posted by jwagman1

Thanks for this!

Cant tell you how many people fight me when i say you gotta remove tune and relock dme. In other states you may get away with it, but no in California!

I am going back to stock this weekend to get my CA Smog. Sucks gotta do it every 2 years from now on, but at least i can do the work myself so its not costly!

What all do you have to do to your car to return to stock? Just curious…

Also let us know if you pass lol. Still on the edge of doing any mods.

cloudyf83 · 11-17-2023, 05:21 PM

has anyone verified that the TCU checksum is something that they checked for? Need to smog really soon, and I did do the BM3 GTS transmission tune. (along with Stage 1, which seems pretty simple to flash back to stock and lock).

whitedc5 · 11-17-2023, 10:17 PM

Quote:

Originally Posted by cloudyf83

has anyone verified that the TCU checksum is something that they checked for? Need to smog really soon, and I did do the BM3 GTS transmission tune. (along with Stage 1, which seems pretty simple to flash back to stock and lock).

I reached out to proTUNING Freaks support and they insist that the transmission tune is not checked during smog. Not sure if they're just not aware of California's process. I don't know who's right or wrong here. Please let us know how your smog check goes...

2sporty · 11-19-2023, 02:10 PM

Quote:

Originally Posted by whitedc5

I reached out to proTUNING Freaks support and they insist that the transmission tune is not checked during smog. Not sure if they're just not aware of California's process. I don't know who's right or wrong here. Please let us know how your smog check goes...

I am also not sure who is right or wrong with what you just mentioned. It definitely did cross my mind that there's a possibility they would not check, but it clearly shows as a mismatch on the TCU's CAL ID/CVN pair when I use my OBD scanner to check.

I talked to bootmod support and they insisted that the CAL ID/CVN is reverted to matching by flashing the TCU back to a stock copy via bootmod. This was clearly not the case when I tried.

cloudyf83 · 11-29-2023, 03:23 PM

ok, just came back from a CA smog check. passed.

I had BM3 DME and TCU flashed. I didn’t want to risk my TCU being mismatched and flagged by the referree, so I contacted kubax86 and he did a fantastic job remotely flashing everything to stock. Highly recommended.

Did the drive cycle. Had the Car scanner app turned on and saw everything go green. Went to smog and everything went fine. Hope that helps!

greysea · 11-29-2023, 04:57 PM

Quote:

Originally Posted by cloudyf83

ok, just came back from a CA smog check. passed.

I had BM3 DME and TCU flashed. I didn’t want to risk my TCU being mismatched and flagged by the referree, so I contacted kubax86 and he did a fantastic job remotely flashing everything to stock. Highly recommended.

Did the drive cycle. Had the Car scanner app turned on and saw everything go green. Went to smog and everything went fine. Hope that helps!

This is amazing! This gives me hope of being able to buy bm3 and do the tune and tcu flash and then return it to stock and pass CA smog!

Thanks for reporting back.

sparkyblue · 12-05-2023, 11:27 PM

Is anyone able to validate that CA smog requires TCU CAL ID/CVN?

Reverting ECU back to stock is easy by uninstalling MHD tune and reverting back to stock.

TCU is the issue now as I installed the GTS Transmission Tune.

M3SQRD · 12-06-2023, 03:31 AM

The state of MD started checking ECU software in 2021 but. However, I had no issue passing with a TCU tune/flash installed.

09-16-2023, 04:16 PM	#1
2sporty First Lieutenant 244 Rep 356 Posts Drives: bmw Join Date: Jul 2014 Location: Munich iTrader: (0)	Guide on how to pass Smog I am writing this to help everyone because I believe the smog check racket, especially in CA, is absolutely ridiculous. I have gathered this information by reading pages and pages of eye bleeding bullshit and a few precious tidbits of valuable information. The rest I had to discover by myself from trial and error. You can find and derive most of this information by searching, but it's scattered everywhere in fragments. To pass CA Smog check, which is the most strict smog check in the country, there are two main conditions: 1) Your CAL ID/CVNs have to match (if you've tuned the car with software, they do not match) 2) All of your smog check monitors have to pass in CA except for the EVAP monitor. 1) What is CAL ID/CVN? It's a checksum for your DME and TCU. If you have made any modifications, the checksum will not match because, by tuning, you have modified bits in the software. After reading many posts on CAL ID/CVN. I initially thought our cars had one CAL ID and one CVN that has to match. Guess what? In our cars there are TWO SETS of CAL ID/CVNs. Why are there two sets? Because one corresponds to the DME and one is the TCU (transmission control unit). If you modified your car with an engine tune, it modifies the DME. If you did a transmission tune (ie: XHP or bootmod transmission flash), it modifies the TCU. Now here's the catch. Some tools don't even make a backup for you, so you cannot get the CAL ID/CVNs to match by flashing back to stock using their tool! Bootmod will get CAL ID/CVN to match FOR THE DME ONLY if you flash back to stock and re-lock the DME. If you flashed the bootmod transmission flash, as far as I know, you're out of luck. The TCU CAL ID/CVN will not match. You will need to flash a stock TCU. I had kubax86 do this remotely and I highly recommend him. You need an OBD tool with mode $9 or ISTA in order to see the CAL ID/CVN. Some crappy OBD tools only show one set for some reason. The Innova 5210 is the cheapest tool I could find that reads all of them. Both sets of CAL ID/CVN must match. The alphanumeric strings have to literally match. 2) After you have flashed back to stock, you need to check your "monitors". Smog check monitors are the checks that your car performs in order to verify that it is emissions compliant. When you do something like reset the DME to stock, there will be about 5 monitors that will show up as NOT PASSED. This does not mean fail, it means that the test needs to be run on them. How do you run the test to make them pass? Do the bmw drive cycle as shown in the image I have attached. I do this with the "Car Scanner" app on the iPhone with the "emission tests" part open. You can see it live as the monitors turn green, into "PASSED" as you do the drive cycle. In California at least, every one needs to be "PASSED" except for the EVAP monitor before you take it in for a smog check. hardware modifications: If you have a downpipe with no catalytic converter (and no way to bypass this check), you will not pass some monitors. visual check: If you have midpipes, which eliminate the secondary cats, you will pass, unless they visually check that the secondary cats are gone. Most stations won't check unless they are super anal or have an incentive to fail you and make you come back and pay again. If your car looks stock, there is generally less of a chance they will check. Not everyone is going to bend their ass down and put their head on the ground on every single car to check. They'll trust the ECU most of the time unless your car (or perhaps you) "looks suspicious". If you drive a car that you can pull up to your relatives and co-workers with while still being able to look them in the eyes, you'll likely pass visual unless the checker is a total asshat. Attached Images Last edited by 2sporty; 09-16-2023 at 04:22 PM.. Reason: add image
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09-16-2023, 07:25 PM	#2
greysea Private 59 Rep 61 Posts Drives: BMW M4 Join Date: Aug 2023 Location: NorCal iTrader: (0) Garage List 2016 BMW M4 [0.00]	Thank you for posting this. I am in northern CA and just recently went through hell selling my lexus is350 and having a wrong carb sticker that was for a 2014 and not my year which was 2015. I am very hesitant on doing any tuning or exhaust mods because it is a real headache. Especially if you get sent to the state ref. So far I have only done cosmetic mods. But I really want to do a bm3 stage 1 tune and get AA EL midpipes or single and call it a day. Doing the stage 1 and midpipes might be worth this headache every two years. I really want that sound plus that hp/tq increase. It is awesome (on paper and youtube vids lol)
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09-17-2023, 07:50 PM	#3
Hxngs First Lieutenant 176 Rep 301 Posts Drives: BMW M3 Join Date: Mar 2019 Location: CA6 iTrader: (0) Garage List 2018 BMW 340i [0.00] 2016 BMW M3 [0.00]	since I have a manual. I only need to worry about the DME matching?
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09-17-2023, 08:48 PM	#4
Wanted_M Captain 759 Rep 950 Posts Drives: Frozen Blue M4CS Join Date: Jul 2009 Location: Norcal iTrader: (2)	Or try Weistec tune stage 1 since its CARB approved. I don't know anyone using their tune but as far as I know, it's the only M3/4 CARB approved tune. __________________ M4CS Frozen Blue ARM DP's/Resonated Mid-pipe \| SPL links \| Hotchkis bars \| JRZ RS2/camber plates \| K&N \| Koyorad HX \| Powerflex purple \| Rouge \| Spiegler \| Speed Eng. snorkel \| Vargas CBC/hub \| Wagner IC \| xHP \| Xpel stealth ppf
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09-18-2023, 11:55 AM	#5
FaRKle! Brigadier General 4016 Rep 3,540 Posts Drives: 328d Wagon, M2 Comp, i4 eD35 Join Date: Sep 2016 Location: Bay Area, CA iTrader: (4) Garage List 2023 BMW i4 eDrive 35 [0.00] 2017 BMW 328dx Wagon [0.00] 2021 BMW M2 Competi ... [0.00]	There's another option for #1, find a tuner that knows how to make the CALID/CVNs match the stock values even with their tune . You won't find this with anybody using a 3rd party platform to tune though (like BM3). __________________ -328d Wagon Build Log (with helpful reference links) -My YouTube Channel for some of the best DIYs and in depth information Please don't PM me for suspension recommendations unless interested in paid private consultations.
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09-26-2023, 09:26 PM	#10
Hotflare Lieutenant 189 Rep 546 Posts Drives: 2018 YMB M3 Comp Join Date: May 2020 Location: East Bay Area, California iTrader: (0) Garage List 2018 BMW M3 [9.50]	Thx For this bro
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09-26-2023, 09:58 PM	#11
bholler First Lieutenant 5341 Rep 370 Posts Drives: 2017 Ferrari Red F80 Join Date: May 2016 Location: Bay Area iTrader: (0) Garage List 2017 Ferrari Red F80 [9.47]	Thank you for all this great information and curated nicely. This jives with my research and held in my head. Bummer to hear about the Transmission CAL ID CVN. Never heard about that one. Not looking for to have to deal with that in 2025. Hopefully there is fix by then. __________________ https://www.instagram.com/ferrariredm3/ 2017 ///M3 Individual Ferrari Red / Full Black Leather/ ZCP / DCT
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10-16-2023, 02:32 PM	#13
Changtownriot New Member 0 Rep 15 Posts Drives: BMW M3 Join Date: Jun 2020 Location: Sacramento iTrader: (0)	I’ve been getting ready to smog my car and did the drive cycle Friday night. Got every monitor to be ready and thought I was good. I was going to take it this Monday morning for the smog check and I figured I should check the monitors again before I go. For some reason all the monitors that were ready on Friday were no longer ready. No idea what would cause this since the car battery didn’t die or anything? Does anyone have an idea of why this would happen? The only thing I could think of is I have a exhaust flap controller that plugs in through the obd port, maybe that caused the ecu to drop voltage and reset? Sounds crazy to me but I’m stumped on what’s going on.
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11-07-2023, 02:42 PM	#14
jwagman1 Private First Class 30 Rep 102 Posts Drives: 2015 BMW M3 Sedan YMB Join Date: Feb 2014 Location: Temecula, CA iTrader: (0)	Thanks for this! Cant tell you how many people fight me when i say you gotta remove tune and relock dme. In other states you may get away with it, but no in California! I am going back to stock this weekend to get my CA Smog. Sucks gotta do it every 2 years from now on, but at least i can do the work myself so its not costly!
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11-17-2023, 05:21 PM	#16
cloudyf83 New Member 3 Rep 12 Posts Drives: 2015 F83 Join Date: Sep 2019 Location: Los Angeles iTrader: (0)	has anyone verified that the TCU checksum is something that they checked for? Need to smog really soon, and I did do the BM3 GTS transmission tune. (along with Stage 1, which seems pretty simple to flash back to stock and lock).
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11-29-2023, 03:23 PM	#19
cloudyf83 New Member 3 Rep 12 Posts Drives: 2015 F83 Join Date: Sep 2019 Location: Los Angeles iTrader: (0)	ok, just came back from a CA smog check. passed. I had BM3 DME and TCU flashed. I didn’t want to risk my TCU being mismatched and flagged by the referree, so I contacted kubax86 and he did a fantastic job remotely flashing everything to stock. Highly recommended. Did the drive cycle. Had the Car scanner app turned on and saw everything go green. Went to smog and everything went fine. Hope that helps!
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12-05-2023, 11:27 PM	#21
sparkyblue Captain 64 Rep 760 Posts Drives: E82 135i & F80 M3 Join Date: Jan 2011 Location: USA iTrader: (8) Garage List 2008 BMW 135i [0.00]	Is anyone able to validate that CA smog requires TCU CAL ID/CVN? Reverting ECU back to stock is easy by uninstalling MHD tune and reverting back to stock. TCU is the issue now as I installed the GTS Transmission Tune.
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12-06-2023, 03:31 AM	#22
M3SQRD Major General 2161 Rep 5,548 Posts Drives: E92 M3,G20 330ix,F22 240iX,F82 Join Date: Jun 2009 Location: Mid-Atlantic iTrader: (11)	The state of MD started checking ECU software in 2021 but. However, I had no issue passing with a TCU tune/flash installed.
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