Tuned ECUs Will Automatically Fail California's Smog Test

Genevieve Fraser
Oct 14, 2021 · 4 min read
Emissions are a hot topic in today's politics and likely won't be going anywhere anytime soon, but the state of California is trying to do what it can with legal action to reduce smog. They recently made changes that impact whether or not drivers can register their vehicles in the state, specifically drivers with Electronic Control Unit (ECU) software tuning.
A close-up of exhaust from a red vehicle’s exhaust pipe
Carbon emissions are an important topic in today’s climate.
The state of California may be one of the most stringent states when it comes to smog testing and emissions restrictions, according to Ford Authority. In order to register your vehicle in California, you must take it for either annual or bi-annual (depending on your car's model year) smog testing at a specified location.
If your car doesn't pass the inspection for any reason, you cannot legally register your car.
For many people, this may come as quite a shock. Many states have no emissions testing and there are no special hoops to jump through in order to register your vehicle.
It's worth noting that, according to MotorTrend, California has the most aftermarket car fanatics in the U.S. Other states with fewer reports of aftermarket modifications may not be as inclined to tighten regulations.

ECU-tuned cars won't pass California smog inspection

In July, California made changes to its emissions testing that impacted many car owners who had aftermarket modifications to their vehicles. As explained by GM Authority, the new changes include an ECU software test to ensure the vehicle has not had any illegal engine tunes. If it has, it will automatically fail the smog test.
Many extreme car enthusiasts regularly use ECU tunes to make software changes to their car's engine. These upgrades enhance the car's ability to run with increased power by utilizing more fuel, resulting in higher emissions as explained by Motor Authority. These emissions are exactly what the state of California is trying to cut out–hence the new rules.
There are still options for those who want to modify their engines and comply with regulations. As long as the ECU tune is approved through the California Air Resources Board Executive Order, the vehicle will still legally pass the test. There are several companies who offer ECU tunes that comply with the Executive Order.

Will the new measures really help reduce smog?

A common roadblock with emissions testing is that reverting cars back to factory settings by removing the installed software is generally fairly simple.
While this is good for car drivers, it is not good for the state of California, as drivers can simply uninstall the ECU tune in order to pass their emissions testing and reinstall the ECU tune immediately after.
There is little that can currently be done to avoid this scenario, but Europe is working towards making the smog emissions rules more difficult to outsmart. They have proposed reducing 1990-level CO2 emissions by 55% by 2030 and are looking to stop the manufacture of internal-combustion engines by 2035 as reported by Motor Authority.
Many people are already opting to go green with their vehicles and even get insurance discounts for doing so. With the push for crackdowns on car emissions, testing and regulations are likely to become more common in the future.
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