DETROIT — General Motors is leaning toward an emissions system, urea injection, which enables diesel engines to meet tough pollution standards in place for 2009, according to Automotive News. The technology, also known as selective catalytic reduction, is used on freight-hauling trucks in Europe. However, the EPA questions the use of selective catalytic reduction because the driver must keep the vehicle from running out of urea. If the urea tank runs dry, the driver will notice no difference in performance. But the vehicle won’t meet emissions standards for smog-producing oxides of nitro-gen, or NOx. GM officials say they will decide in the next 12 months whether to install the urea injection system on heavy-duty diesel trucks in North America. The alternative, a filter in the exhaust system called a lean NOx trap, also is being evaluated by GM. The urea injection system works by shooting an ammonia-like acid into the exhaust pipes, reducing NOx. Because engineers need two to three years to design, develop, integrate, test, and validate an emissions system, GM must decide soon which technology it will install, according to the Automotive News report. Starting in 2009, emission standards require diesel engines on heavy-duty trucks to run as cleanly as gasoline engines. If GM doesn’t have a new emission system ready when the tougher rules go into effect, it could cost the company billions of dollars in lost sales on the Silverado and Sierra.