A ban on diesel engines built prior to 1988 took effect Jan. 1 in the Greater Phoenix area, according to the Arizona Republic newspaper. The ban applies only to trucks registered within the Greater Phoenix area, and to all diesel engines in vehicles rated at 26,000 pounds GVW or more. An estimated 3,000 such vehicles in the metro area don't meet the new standard.The law was passed in 1996, but did not go into effect until 2004. In 1996 lawmakers intended to help clean up the Valley's air pollution by outlawing heavy-duty diesel engines built before 1988. Those engines kick out an unhealthy dose of particulates, a visible pollutant proven difficult to erase in the greater metro area. According to the Arizona Republic, as many of the 2,000 or so small operators aren't prepared for the engine ban.Arizona Department of Environmental Quality (ADEQ) officials said truck owners who can prove at the emissions-testing station that they have ordered the parts needed to make their engines comply or are on a waiting list to get the needed repairs made will be granted a one-year reprieve.Otherwise, trucks with pre-1988 engines that fail the emissions test will not be given auto registration.When fully in effect, the engine ban is expected to cut particulate pollution by 1 ton a day. Approximately 350 tons are pumped into the air of Greater Phoenix each day.