What California's New ECU Law Means for Tuned Cars

California's biennial smog check now includes a test to detect unapproved ECU software or aftermarket tuners. We spoke with a SEMA representative to find out what this means for your car.

nsx pops a fireball
Casey Boyle

Last month, the California Bureau of Automotive Repair (BAR) began enforcing a new policy focused on computer tuning in modern electronically-controlled engines. Basically, under the new rules, any vehicle with an ECU that's not approved by the California Air Resources Board (CARB) will fail the state's mandatory biennial smog check. When the news first broke, automotive enthusiasts in California and elsewhere voiced concerns about the new limitation, and wondered how it might affect tuned and modified vehicles. To get a better understanding of the new rules, we spoke with SEMA director of emissions compliance Peter Treydte.

In California, every registered vehicle has to pass a biennial smog check, which includes visual inspection of emissions equipment and a tailpipe test. The tests impact all gasoline-powered passenger vehicles from 1976 onwards, and every diesel-powered passenger vehicle from 1998 or newer. Testing is not required on vehicles that are less than eight years old.

As of July 19, 2021, BAR will expand this testing procedure beyond the standard visual inspection and tailpipe test. Now, OBDII-equipped cars and trucks from 1996 or newer will be checked to make sure they're running factory software or a CARB-approved ECU tune. If a car is running software that does not fall into these categories, it will fail the smog check, and can't be registered or renewed until the computer equipment is brought into compliance.

Testing for compliance involves plugging into the car's ECU and checking for two pieces of data: The Calibration Identification, or Cal ID, and the Calibration Verification Number, CVN. The Cal ID indicates which version of the software the car is running, similar to the iOS number in your iPhone. The CVN is calculated based on how the car runs, using parameters studied by the ECU, with the number changing when the software is adjusted.

California's new test looks at the CVN and Cal ID figures in the ECU’s code to determine if anything is out of place. (This suggests that certain "piggyback" devices could skirt the test if they're not detected visually, as these inline tuners don't change the Cal ID or CVN.) Any aftermarket computer device, whether it's an ECU or an inline tuner, is required to carry an Executive Order number, or EO, that indicates it's been approved by CARB.

CARB and BAR have yet to clarify what this new test procedure means for vehicles built before 1996 (i.e., pre-OBD), though the state requires all cars built after 1975 to pass the emissions test for their model year. What we do know for sure is this: if you’re running an ECU or a tuning device that doesn't have a CARB EO, you’re gonna want to bring it back into compliance before your next emissions test.

Treydte and his colleagues at SEMA are no strangers to BAR and CARB. In fact, a large part of SEMA's work involves collaborating with regulators on things like emissions compliance. As a result, Treydte has become quite knowledgeable about this new regulation, and feels strongly that there's no reason for enthusiasts to fear the new tests.

"So far in the two weeks that have transpired, we have seen zero instances of concern," Treydte told R&T. "I really don’t think that this is problematic."

The SEMA executive explained that only a tiny number of California vehicles are likely to be in violation of the new rule. Treydte says BAR shared data with SEMA estimating that, out of the roughly one million vehicles that undergo smog testing each month, only around 150 to 300 cars are expected to fail due to an illegal ECU tune. For comparison, around 10,000 cars fail every month due to mechanical problems or other non-ECU issues. These estimates should be trustworthy: BAR has had the authority to run this program in California since 2013, and has been collecting data on the ECUs of cars being tested since 2015.

That data has shaped the rules that are now being implemented. Treydte says the data BAR has collected can tell the agency how many vehicles are factory-tuned (i.e., with a post-purchase computer update) and which are running aftermarket software or computer hardware. "They know which of those aftermarket modifications are legal, associated with a CARB Executive Order," he said. "They already have that information. What’s happened here as of July 19 is simply an implementation of a failure condition during smog check based on some of that data they read from an ECU."

SEMA has worked closely with aftermarket suppliers to get a significant number of tuning devices CARB EO-certified. Of the nearly 500 CARB EOs that SEMA has gotten certified over the last eight years, the majority have been related to ECU tunes, including those that come with certain forced-induction upgrade kits. SEMA isn’t alone in this effort: Aftermarket equipment makers can get their products certified on their own if they’re willing to go through the process. A full searchable list of CARB EO-certified parts can be found here.

Not every aftermarket parts manufacturer is interested in playing by the rules, of course. Treydte said some are likely fearful or ignorant of the process of EO certification, while others are willing belligerent when it comes to the rules. Those in the latter category, particularly those involved in diesel truck tuning, are largely responsible for the new rules.

"When you do certain egregious things with modifications, you can create a situation where the [emissions] output of a given vehicle can be ten, 15, or 100 times what that vehicle might have been in its stock form," said Treydte. "With diesel pickup trucks for example, removing emissions systems through EGR deletes, not only are you creating a much higher output of emissions, but it's also very visible. You get soot coming out the tailpipe. It shines a spotlight on certain modifications that make our industry look bad.... We’re trying to educate our industry that these things can not only be detrimental to air quality, but also to our reputation."

In Treydte's view, with electric cars growing in popularity, a reputation for environmental recklessness is the last thing the automotive aftermarket needs. By collaborating with regulators, SEMA hopes to forestall a situation where the EPA clamps down on the tuning industry on a national level—something Treydte fears could happen if the non-compliant segment of the aftermarket continues to flout the current rules. And now that you know the law, you're better equipped to make sure your car will pass its next smog check.

This content is created and maintained by a third party, and imported onto this page to help users provide their email addresses. You may be able to find more information about this and similar content at piano.io
Advertisement - Continue Reading Below
More From Car Culture