CA/LA Smog

[Tbonem3]

Flashing back to your original factory file should be fine. BAR even said so, I think I remember reading in one of the posted links.

[2004LSB]

Pardon my ignorance on coding and tuning, but hypothetically if one were to reflash canned tunes back to the factory / default tune, this shouldn't create any issues with the CVN / checksum data correct? How about swapping ECUs with a virgin one?

[siamkazi]

Just a heads up to the guys who aren't as computer savvy... ANY changes done to the dme will technically change the checksum. So yes even if you enabled sport mode memory, you technically will fail. Honestly I think its only a matter of time till this gets thrown out in court for being overly ridiculous. Anything modified in the dme that doesn't impact emissions in any way, shape, or form and cause you to fail smog. That includes even an smg tune where the shift parameters were modified on the dme side. SMG unit flash would be unrelated. But yes this is beyond ridiculous.

Thank you for this, I am not ashamed to admit that I was googling terms/abbreviations more than I would like to admit 😂

On a more serious note, this is no bueno at all. Curious to see how the next 30 days pan out for others (including other makes/models i.e. GTR's Evo's etc).

[repoman89]

It's calculated. Exactly how it's calculated isn't entirely clear to me. IIRC @gpetersen found that if you brute force the checksum such that the calculated checksum is equal to the stock value, then the CVN is also correct. So it's either itself a CRC16 (of each half) with a different initial value and/or polynomial, or it's some sort of calculation that's done to the calculated checksum.

Probably wouldn't be crazy difficult to hardcode the program to return a valid value

That’s my recollection as well, and looking at some notes the checksum is also calculated in a strange way (reorder each data segment half minus the last two bytes of the first half, get CRC16 on that, write it in the location of the two removed bytes). I saved p0lar’s Perl implementation of that calculation from the old forum and was going to translate to python to make a brute forcer tool … too lazy to do the actual math. I have the main part of the brute forcer script, including a table of cal IDs vs expected CRCs that I pulled from the old forum, just needed to get the checksum calculator right. There are lots of long sequences of zeros in my binary at least, figured it’d be harmless to use a couple of them to force a collision

I started all that in 2019 because there were rumors that MA was collecting CVN data to flag if it changed year over year .. don’t think anything ever came of it, and also they’re oddly lax about OBD2 emissions, exempting anything 15 years or older.

[IamFODI]

Mods/admins just deleted some political commentary and otherwise uselessly contentious posts. Please, everyone, let's remember why we're here.

[thegenius46m]

Just a heads up to the guys who aren't as computer savvy... ANY changes done to the dme will technically change the checksum. So yes even if you enabled sport mode memory, you technically will fail. Honestly I think its only a matter of time till this gets thrown out in court for being overly ridiculous. Anything modified in the dme that doesn't impact emissions in any way, shape, or form and cause you to fail smog. That includes even an smg tune where the shift parameters were modified on the dme side. SMG unit flash would be unrelated. But yes this is beyond ridiculous.

[terra]

If we can disable CRC check and modify the CVN and Cal ID to that of virgin stock tune parameters, this will be easy to bypass by spoofing. I'm thinking just mirror all these checksum parameters in the tune file (pic below) from the reference tables in the mss54 master page to match a virgin tune then just roll up lol. If its possible this will create some insane demand. Think of all the manual swap cars on hacked tunes.

Only other option is to do what repoman suggested which would be to modify unused sections of the tune to adjust the checksum calculation to match the virgin cvn number.

CRC check is easy to disable, but the CVN is still calculated (I.e the tune doesn’t just grab the stored checksum value to derive the CVN).

Forcing a CRC collision is relatively simple, that can certainly be done. 16-bit is small enough that it can be brute forced instead of doing the actual math to calculate a collision.

[shibui]

The only thing I did to my car in terms of software was a TTFS SMG tune way back when. Would something like this cause me to fail under these new rules?

[DropTopKingM3]

Catless down pipes and burble tunes is what got us into this mess. TY newer BMW guys 🤦♂️

[erickhoyos]

Anyone got the plug for smog somewhere in the Bay Area? Desperately need it asap as my registration expired

[Samsonite79]

Sounds like the perfect opportunity for someone to start a rent-a-dme service. They would just need a non-HP and an HP that they flash with the appropriate software for the car it's going to.

BMW BLOCKBUSTERS?

BTW I might offer some kind help/service if you're in dire need around the SF Bay Area region, let me know through PM, I'll try my best.

[heinzboehmer]

Sounds like the perfect opportunity for someone to start a rent-a-dme service. They would just need a non-HP and an HP that they flash with the appropriate software for the car it's going to.

[sev]

Sevan, ask your boy if there's any mention of year cutoffs specifically mentioned.

he said all OBD2, but i dont think he specifically knew. he did mention theyre going to get extremely strict on aftermarket cats based on the test group number under the hood.

[timmo]

Yeah, I'm moving to Cali this fall. Great timing too, since my SAP just failed. If I was staying in Ontario I'd delete it, but I found a couple real cheap pumps off a salvage yard on eBay as replacement. Freaking Ontario just got rid of e-testing, now I have to go back to it

[thegenius46m]

I might be one soon enough

Think of all the guys who did smog legal swaps verified by BAR with a different dme than what came with the car which is now "unlocked" because no one actually bench flashes to realign ews the proper way. EWS delete or any variant of a manual swap where any sensors were forgone to complete the swap where a software change was made to adjust for the sensor not being used gear position sensor for instance, you are fucked. Same as if you had your current tune modified for a manual swap. Has nothing to do with emissions but for these asshole's sake, it's now considered a "tuned car" that will fail the checksum, which is utter bullshit.