Congress created a program that helps pay for cleaning up older diesel engines, such as those in trucks, buses, boats, and construction equipment, which give off air pollution. The program is run by the Environmental Protection Agency (EPA), the federal agency that sets and enforces national pollution rules, and it offers grants, rebates, or loans to cover the cost of either replacing an old diesel engine or adding equipment that reduces the pollution it puts out. The bill extends the program's legal authorization through the 2029 budget year, so the EPA can keep offering that help until then. The summary doesn't say how much money would be available or who specifically would qualify, so those details would come from other parts of the law or from later funding decisions.