From July 19, 2021, California will start testing for non-approved ECU tunes during its biennial Smog Check program.
First spotted by Car Bibles (via Road & Track), the rules state that any software not provided by the car's manufacturer or approved through a California Air Resources Board executive order will fail the test. Details of the test procedure haven't been mentioned, though it will likely be via a check of the car's OBD II port.
All hope isn't lost if you live in California and have indeed tuned your car. If you can have the original software the car came with plugged back in, you can use it to pass the test.
ECU tunes are a common mod for anyone adding upgrades to an engine. They typically involve the engine burning more fuel in a quest for more power, and this of course will result in extra emissions.
The crackdown emissions also took a new step over in Europe. The European Union's executive branch, the European Commission, on Wednesday announced a number of proposals aimed at curbing emissions. One of them was a target of a 55% reduction in CO2 from 1990 levels by the year 2030, and this would rise to a 100% reduction for cars by 2035.
That 2035 target would mean no new cars would be available with internal-combustion engines, hybrids included. And according to the proposals, current CO2 exemptions for smaller automakers production less than 10,000 cars per year would be removed as well.