The U.S. Environmental Protection Agency on Tuesday issued new guidance that allows diesel-engine and equipment manufacturers to revise software governing Diesel Exhaust Fluid systems, extending the time operators have to correct faults before engines are forced to slow or shut down. The policy, announced by Administrator Lee Zeldin at the Iowa State Fair, instructs companies to widen warning periods to as much as 650 miles for heavy-duty trucks and 36 hours for farm equipment before any power reduction occurs, a sharp increase from the current four-hour window. EPA said the change maintains existing nitrogen-oxide emission standards while reducing unexpected downtime for trucks, tractors and other machinery that rely on selective catalytic reduction technology. The Small Business Administration estimated the looser inducement schedule will save U.S. farmers about $727 million a year by cutting towing, repair and rental costs, with additional but unspecified benefits for trucking and construction firms. The move comes as the Trump administration continues to roll back regulations it says hamper productivity, even as it pledges not to compromise air-quality goals. In a separate development underscoring regulatory uncertainty for heavy-duty vehicles, Daimler, Volvo, Paccar and International Motors sued California in federal court, seeking to bar the state from enforcing its tougher emission rules. The manufacturers argue they are "caught in the crossfire" after President Trump in June revoked federal waivers that had allowed California to impose stricter limits on diesel truck emissions and accelerate sales of zero-emission models.