California’s New Smog Check Rules Spell Trouble for ECU-Tuned Vehicles


Have you ever wondered why the Volkswagen Golf with the 1.5-liter TSI four-cylinder turbo is available with 130 and 150 metric horsepower for the 2021 model year? I haven’t either, but hear me out. Those TSIs are pretty much the same between them, save for the ECU’s software.

How can a few lines of code bump that engine by 20 ponies, you ask? It’s a relatively straightforward affair because the engine control unit dictates how much fuel is channeled to the injectors, how the ignition operates, and so forth. As opposed to the good ol’ days when a beefier carburetor and a more aggressive camshaft were enough to improve horsepower and torque, cars from the modern era can easily make more oomph with an ECU reflash.

Be that as it may, California lawmakers don’t like the aftermarket community too much. The Golden State’s Smog Check program will change from July 19th for the worse because “vehicles with software not provided by the original equipment manufacturer or approved through a California Air Resources Board executive order will fail the Smog Check.”

Considering that California sets the stage for the rest of the United States in terms of emissions regulations, other Smog Check states are likely to follow suit in the near future. There is, however, a workaround for this hindrance.

The Bureau of Automotive Repair highlights that you must have the vehicle’s software restored to the OEM software before a Smog Check, which brings us to another advantage of ECU tuning over hardware mods.

I won’t give any names because this isn’t a sponsored article, but most ECU tuners available to purchase in the United States allow the user to return to the factory settings at any given time. But there’s another problem worth mentioning, and that’s the Calibration Verification Number (CVN) that makes it easy for the Smog Check referee to find out if the software has been changed for more oomph or reverted back to the original specification.

On that worrisome note, what do you think about this change?