ECU Tune and Failed Emissions Testing Experience

One last final massive update. OTT tune got their CARB approval making it the only NA tune for the Tacoma that is 100% CARB approved and will pass any emissions test that is now checking for a modified ECU. Big shout out to @JustDSM and the team for working hard on getting us tuned Tacoma users legal. I've had my tune for around 8 months now and it is still one of if not the best mods to my truck. Thanks, OTT!

Hi TW, I wanted to share my experience with getting my truck tuned and failing my state's emissions test.

I recently posted in another thread about this and wanted to do a more comprehensive write-up.

I wanted to get some things out of the way first. Although this whole process took a lot longer than expected and cost me more money than expected, I don't hold any fault or blame on any party. In addition, I also live in CO and our pollution can get so bad here due to thermal inversion that I understand the need for emmisons regulation. This isn't a political debate, rules and laws are just that and if you don't like them well then go try to change them. Until then follow them, work around them, or break them but be prepared to pay the price. I decided to work around them.

Huge update: The man himself @JustDSM posted documentation showing the OTT tune has acquired SEMA Certified Emissions and is on its way to getting a CARB EO#. See post 180 here. Once OTT gets this EO#, any Tacoma with an OTT tune that gets emissions tested with a CVN check will pass without any hesitation. Thanks to Justin and the OTT team for their hard work and diligence.

So here we go!

I recently purchased a bone stock 2016 Toyota Tacoma TRD OR from my Father in August of 2023. We have been working out the details for a while now and during that time I created an account here on TW and started doing research. I stumbled upon a thread talking about the OTT tune and decided that was going to be my first modification. I traveled back to the Midwest to pick up the truck from my parents. Drove it 1,000 miles back to where I live out in Colorado. On that drive, I got really familiar with how terrible the programming is for the transmission. Once I got back I made an appointment with my local tuner for the following weekend.

I want to shout out Adam with Colorado Toyota Tuning. They are the ones who did my initial tune and helped me through this entire process. I got the tune done. Painless and took no time. I immediately felt a difference and was very satisfied with it. My MPGs went up on my work commute averaging about 23-26mpg. Everything was great, that is until I went to get my title transferred and my vehicle registered.

Like I said before, I did my research. I knew that my vehicle had just become eligible for required emissions testing in 2022. In CO, once your vehicle is 7 years old, you are required to get an emissions test biannually. Looking at the OTT tune and that thread, my confidence was high that the tune would not affect the outcome of my emissions test. Reconfirmed when I went to get the tune done, and double-checked one more time on OTT website. Again, confidence was extremely high. I went through the emissions testing center without a single concern. They were finished and waived me out. I paid, and they handed me the paperwork, starting to say, "You're good to g...., wait a minute, it looks like you failed." They highlighted the test results and handed me the Emissions Test Results as seen below.



They explained to me that I needed to make an appointment with a state emissions testing technical center to figure out what was wrong and that I could not come to any emmisons testing facility for a retest until I did so. They blacklisted my VIN in their system. Great. I texted my tuner and let him know what was up. He gave me a call and we reviewed the test results together. It didn't give us much info as to why it failed. I had no CEL and couldn't imagine why the OBDII port would be failing. So I went ahead and made an appointment with the tech center hoping that they would be able to tell me more.

I went in for my appointment. I met the tech assigned to me, he took my keys, and pulled the truck into his bay, while I hung out in the waiting room. I had just settled in for what I thought was going to be a bit of a wait. I was wrong. He came back in within 5 minutes with some papers and sat down across from me. I have to give this dude credit as he was very patient with me and my countless questions and thoroughly explained to me what exactly was going on.

The first thing he asked me was if I had a tune on the truck, and I simply played dumb. I said I just bought it used and the seller didn't mention anything about a tune. He went on to tell me as soon as he plugged into my truck's OBDII port he could see that the CVN/checksum did not match what was listed for my particular vehicle reported by the manufacturer. The tech said that because my CVN did not match, my truck failed the emissions test. He told me that as of July 2021, Colorado adopted California's emissions testing standards and that part of their new standard is that if the CVN doesn't match what is reported by the manufacturer, it is indicative of a modified ECU, and is an automatic fail. You can see CA's law here.

Note: This new criteria is checking for any modification to the ECU. Any tune or modification to your ECU will change the CVN. This isn’t specific to the OTT Tune.

Below you can see the results of their evaluation.


So that was it, the only reason for failure. It doesn't matter that I was getting way better gas mileage or that the truck was more efficient. In the eyes of the State, my ECU was modified so my car wasn't eligible to be registered. So I asked the tech what I should do, even though I simply knew that I could get my tuner to flash it back to stock. The tech told me I would most likely need to purchase a brand new ECU from a dealer and have to have it installed and programmed with my VIN to disable the immobilizer. He warned me that it could be costly and that if the dealer had any questions to just call him. I heeded his warning grabbed my keys, hopped in my truck, and left. I immediately got on the phone with my tuner and told him what was up. We scheduled a time for him and me to meet so we could try flashing it back to stock.

And that is what we did. We got it flashed back to stock and Adam went to check the CVN/checksum. No dice. At the time the CVN/checksum still didn't match what was stock even though there was no tune on the ECU. EDIT: This has now been fixed as per Colorado Toyota Tuning comment below. I was starting to get a little worried at this point. Adam reassured me that they would get me taken care of. He explained that he was working with a guy who was trying to get the CVN/checksum to revert back to what stock displays but they were still working on it and just starting to test this out. I was driving around an unregistered truck so I didn't really want to wait for this solution. So Adam offered up a temporary solution. He said I could borrow an unmodified ECU from him, we could swap it out, reprogram the VIN to the ECU so the truck could start, and I could take that to the emission technical center and retest. Good solution, the only issue is that I have to retest my truck every 2 years. I didn't want to deal with the hassle of getting a stock ECU from my tuner and having them programmed in my VIN every two years let alone run the risk of them closing down shop at some point or me moving away.

So I told him I would just buy an ECU and keep it. That way I can leave the tuned ECU in my truck regularly and simply swap in the stock one once every two years when I have to get retested. This was the winner. To me, this solution seemed like the best option moving forward. It was futureproof, easy, and I didn't need to rely on any company or anyone to get emissions done. So we made the plan. Adam put the tune back on my truck as I didn't want to be without it and I started looking up where to source an ECU. This all seemed like a great plan until found out how much a new OEM ECU was.

For reference, I already paid the average price for the OTT tune, and to find out that an OEM ECU was going to be an additional $700, I was starting to regret my decision. Unfortunately, due to the nature of this problem, reverting back to stock wasn't an option, and not ponying up for an ECU wasn't an option either. So forward we go. I pulled the part number for my ECU in my truck. The part number for my 2016 AT TRDOR was 89661-04K51. So I hopped on https://www.car-part.com/ punched in what I needed and....nothing. So I went ahead and changed it to a 2017 TRDOR AT redid the search and boom, some results. I found a reputable junkyard and gave them a call. An extremely helpful man answered and was able to tell me that my part number was interchangeable with a few different ones from different model years. So in my case, and for any 2016-2017, any ECU with the following part numbers would work.

89661-04K50
89661-04K51
89661-04K52
89661-04K53
89661-04K54

For reference, if you have a manual then your ECU would be the following part number for 2016-2017.

89661-04K60
89661-04K61
89661-04K62
89661-04K63
Note: The part numbers for model year 2018-2023 are different.

Luckily, they had one of the compatible ECUs in stock and it was only $200. Way more palatable than $700. So I paid, they pulled it, and shipped it my way. 5 days later it was in my hands. I let Adam know and he sent me some instructions on how to swap it and the procedure to resync the immobilizer. The actual swap was pretty easy, for those that don't know, the ECU in our trucks is behind the glove box on the passenger side. Here is the video he sent. Took me about 30 minutes with no issues. I reconnected the battery and continued on to re-syncing the immobilizer. The truck will not start with a new, used, or anything but a stock, paired ECU. So you need to follow this procedure to resync it.
Note: As reported by BLTheP in the comments below, this process changed for model year 2020-2023. You can find more info about it in this thread.



Again, pretty painless. Now the last step in this whole process is to get the ECU programmed with my VIN. I met up with Colorado Toyota Tuning one more time and they got the VIN on the ECU. Finally, I was ready to go pass my emission test. Not so fast! Since I just put a "new to my vehicle" ECU into my truck, I needed it to complete a drive-cycle so the readiness status of all my emissions monitors show ready, otherwise, I could fail another emissions test. If you care to read the procedure to perform a drive cycle you can do so here. After reading the steps, I said forget about it. Adam told me that I could just drive my car around normally for about a week/1 tank of gas. So I did. After spending all the money on this tune, all the time to get the fixed, I was back to driving this truck with its sluggish, anemic, transmission for another week. Needless to say, I couldn't wait until my emissions test appointment at the tech center.

I pulled in, met the same tech I met with the first time around, and told him I simply got a new ECU. He took the truck into his bay, ran his tests, and came back to me with a clean evaluation. I thanked him, got in my truck, and went directly home to immediately swap my ECU back to my tuned one. I wrapped the stock one in some bubble wrap, put it in a box, and stored it away as I wouldn't be needing it for another two years.

I hope that if anyone else experiences the same issues I did they will find this thread and hopefully find this information useful. If you have experienced this, leave a comment. And if you have any questions for me, just fire away and I'll try to help the best I can. I have no animosity for OTT or Colorado Toyota Tuning. OTT makes a great product that I didn't want to be without and the guys over at Colorado Toyota Tuning went above and beyond helping me get this issue solved. I do not regret getting my truck tuned and would do it all over again!

That's all the info I have to share on my experience. I did want to talk a little bit about the whys of all this. Why haven't we heard about this more? Why haven't more people come forward with a similar experience?

When I first experienced the initial failed test I did some research on this form and a few other places to see if anyone else ran into this issue. After hours of digging, I really couldn't find much. It seemed like I was really one of the first to run into this. Adam with Colorado Toyota Tuning reinforced this idea by sharing that he hasn't seen this become a problem at all either. Which left me puzzled. How could nobody else run into this issue? Do these tuners know about this? Are my claims substantiated enough to share this with others?

Well, I spent some time doing some research, reading, and some critical thinking and came to my own conclusions. I think there is a combination of things at play here.

1. These new emissions testing criteria are very recent changes. The law went into effect in July of 2021 in CA and CO. That was two and a half years ago. Depending on when your car was registered you may not be required to test for a year or two after this went into effect.
2. My Truck is the first model year of the Gen 3. It just became eligible for emissions testing late last year. An overwhelming majority of the Gen 3 Tacomas made still don't qualify for emissions testing and won't for a few years. So our sample size is small and the sample size for the single model year that needs testing and has a tune is probably next to nothing.
3. During my research, I came across a whole community with older tuned VW Golfs who immediately ran into this exact same issue ever since the criteria changed. The checksum doesn't match the stock number. It just seemed like the timing with the production of the 3rd Gen, the timing of the change of the laws, and the 6/7 year emission rule all perfectly aligned to keep this issue from rearing its ugly head. Unfortunately, now we seem to be a the very beginning of it for us tuned Tacoma owners.
4. Right now this is really only an issue for people in states that do emissions tests that have CVN/Checksum criteria on their test. What is unfortunate is many states are talking about adopting CA's emission testing standards so although it isn't an issue now, it could be for you in the future.

EDIT: It looks like OTT has worked out how to flash the ECU back to stock and read the correct CVN. This is one of the two currently known workarounds and is probably considered the easier one of the two. I'm unsure if OTT has a software workaround for this or if they even have a response to this at the moment. I hope they get it figured out or at least find an easier workaround for others. Until then, I'll offer whatever assistance I can.

Edit: I wanted to include some links to some info I found when researching this all.
What California's New ECU Law Means for Tuned Cars
Information regarding CVN and CAL ID
What is a CVN

 

Very nice informative post. Unfortunate for those who are tuned in the locations where it matters. I even flashed myself back to stock but if I were in Colorado I'd be in trouble too (once the years pass anyways). Hopefully Texas never follows suit, I doubt they will considering they're about to ditch safety inspections, but emissions will remain so it is not necessarily set in stone that rules like this could never pop up in the future.

All I have to add is that I believe starting somewhere around September 2019, the process to pair the ECM to the truck changed per this post. Apparently need to use Techstream now. Not that it matters yet, but probably will eventually as the newer years become older and surpass the age requirement.

 

Dang. That's a heck an an experience. Well put though! You know what's funny though, for years here i've heard folks say "just flash back to stock, the dealer wont know you have a tune". Sounds like it's not that difficult. If anyone ever thought Toyota couldn't potentially jam you up for warranty work for a tune, i would think again.

Glad you got it sorted sorted out OP.

 

Good info. The emissions testing in IL is a joke. My catless Mustang passes with some 50 cent resisters soldered into the rear 02 sensors. One more test before I can register it as a classic and no more testing.

Funny enough I'll likely put the cats back on it shortly. As I've gotten older I no longer like it smelling like a lawn mower.

 

This should be a sticky... Great Information.

 

Thorough and well written, and glad we could be of help through the process! Unfortunately now we have seen a few of these pop up, but I think your thesis on the 7 year mark/production is spot on.

Just to clear up one part too, the part about the CVN not translating as stock after tuning to stock was a result of encrypted code within the stock file (apparently to prevent a company in I think Australia from ripping off VF’s mapping). No one knew it was an issue unfortunately until this came up. OTT/CTT would never use a program that overrides CVN or causes it to read differently than what it is/would never cheat emissions etc.

The good news is the developer has since got it fixed with the help of a few people/OTT, and OTT tuners can flash the stock file that reports the true stock CVN. The DIY route you went is of course a rock solid option, since they are cheap on car part, and we can of course program the VIN to it should anyone need. But tuning to stock is now also an option thankfully.

 

Hey Adam, that's great to hear! A whole lot easier now than what we went through. This also could have been at least delayed if I went and got it tested before getting that tune. Thanks again for all your help.

 

Is this something anyone can do or something specific to OTTs collection of stock calibrations? I flashed myself back to stock 8 or so months ago and have no idea if my CVN matches or not. Curious if there’s anything that can be done to check and fix on my end if necessary.

 

I'm one of those with an OTT Tune and very happy with my decision.

I've taken it to the same dealership in Delaware since the tune was done and neither party has mentioned anything during the visit.

Whether or not the tune was identified by the dealership, it was never discussed.

I've had discussions with my tuner and take documented experiences written here on a case-by-case basis.

Any questions I have will be directed to my tuner with regards to what has been reported.

 

One reason that this issue hasn't popped up more here in Colo. is that there are only 9 counties in the state that require emissions testing on gasoline vehicles.

**Mod edit for correct information**

• Boulder
• Broomfield
• Denver
• Douglas
• Jefferson
• Portions of Adams
• Portions of Arapahoe
• Portion of Larimer
• Portions of Weld

 

Just move to Jynah!

 

Wow, quite an ordeal.

Im so happy they stopped doing emissions testing about 10 years ago up here.

 

I'm glad I transplanted to the east coast/tri-state area.

Had I stayed in SoCal/LA, I'd be dealing with a lot of crap.

 

I just got through dealing with this on my wife's previously tuned Mini Cooper S.
The test just reported that they couldn't read the catalytic sensor. Since people do delete the cat on Mini's, I thought I got a bad tune. I ended up taking it to the dealer who flashed it stock for $200. Passed today at the tech center. I still have the tune on my laptop, so back it goes for the next 2 years.
I plan on selling the Mini by then.

 

I fear that testing in Utah (similar emission requirements every other year) will yield the same result. I've been driving with the ECT button depressed and happy with the result, shift-wise on my AT.

 

I guess, my question is, was it really worth it?

 

I belive it should be corrected inside of vftuner since the stock calibration is part of the software. But the goal posts were move a few times on regular joes.

 

If one has a tune on one's vehicle, what is the easiest way for the owner (i.e. me) to check the CVN on my ECU? I'd rather do this before going in for emissions testing than after.

I have a good bidirectional scan tool (Autel MS906TS) as well as an HPTuners MPVI2 interface + license for my vehicle -- can I get the CVN with either of these tools? Where is the list of authoritative stock CVNs by year/make/model/trim etc. to compare my result with?

 

I’d be lying if I said this didn’t make me a little nervous about the possibility of being declined any warranty work if I were to have powertrain issues. If it’s that easy for them to see the CVN, I’m assuming the dealer is no different?

 

The CVN topic came a few times in the past, but we were under impression that the stock tune file was the way to stay compliant with regs. Finding out the news that the file is effed is not a good news.