California promises to sniff out automakers cheating on emissions. In a letter to manufacturers sent Wednesday—first reported by Reuters—California’s Air Resources Board (CARB) urged them to fess up about non-compliance and other emissions-related violations by the end of the year.

Otherwise its new testing laboratory, to open next year, will “inevitably detect any violations you may have,” it warned. 

California tends to have stricter vehicle-emissions rules than the federal government. And now, with a lung-related pandemic and a record year for forest fires helping build awareness of the public-health impact, CARB won't tolerate excessive tailpipe emissions.

The 2015 Volkswagen diesel scandal centered around software-based defeat devices that identified when a vehicle was being run through a test cycle, changing its parameters to run in a leaner, perhaps rougher-running mode than users would likely ever encounter in real-world use. 

Since then, Daimler and Fiat Chrysler Automobiles have also paid penalties related to defeat devices, and CARB notes in the letter that it’s already collected more than $1 billion across multiple settlements. 

2014 Mercedes-Benz E250 BlueTec 4Matic

Meanwhile, the state’s electric vehicle mandate has progressed, as more states have signed on despite a challenge of its authority by the Trump administration. Last month governor Gavin Newsom took the mandate to its logical next step: a goal to ban the sale of new gasoline-powered cars in the state by 2035.  

The letter made no statement or claims that it is currently aware of such defeat devices in current models, but it noted that “voluntary disclosure will trigger a reduction in penalties; failure to do so may affect the result of future enforcement actions.” 

If companies don’t come forward by the end of the year, they might face an increased maximum penalty of $37,500 per mobile source or engine, per identified violation. 

The warning wasn’t aimed entirely at automakers; it also applied to companies making medium- and heavy-duty trucks, as well as motorcycles, marine engines, and recreational vehicles.