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Engine, equipment and emission-control manufacturers will need to keep their lines of communication open for the next several years as regulators focus on their next target in the never-ending push to reduce emissions. Regulators want engine manufacturers to incorporate on-board diagnostic systems into their electronic controls. These systems won't do anything to reduce emissions. Instead they will prevent an increase in emissions by alerting operators when diesel particulate traps, oxidation catalysts and other aftertreatment components begin to fail.

On-board diagnostics has been installed on cars and light-duty vehicles since the early 1990s, but are just now making their way to commercial, diesel-fueled vehicles. In December, the federal Environmental Protection Agency (EPA) proposed regulations requiring the diagnostic systems be on diesel-fueled trucks starting in 2010, and indicated its intent to follow up with similar requirements for off-highway equipment.

The EPA's proposal is not surprising given the evolution of emission-control strategies. Until now, engineers have relied on engine modifications and electronic controls to drive down emissions. They altered the engine timing, modified the piston and combustion chamber, and added electronic controls and charge-air cooling. After accomplishing virtually all they could in these areas, engineers turned their attention to treating exhaust gases, using technologies such as exhaust gas recirculation (EGR), diesel particulate filters and NOx catalysts. Because these components can fail without compromising engine performance, regulators want to ensure that operators and fleet owners are alerted to any malfunctions that would increase emissions.

"Heavy-duty engines, particularly diesel engines, have very long, useful lives," the EPA's proposal notes. "With age comes deterioration and a tendency toward increasing emissions. [On-board diagnostics] will help to ensure that engines and emission components will be properly maintained and will continue to emit at low emissions levels, even after accumulating hundreds of thousands and even millions of miles."

Engine manufacturers required to develop systems

As with virtually all of the other emission control strategies to date, the ones for meeting the on-board diagnostic requirements will fall on engine manufacturers' shoulders. Truck manufacturers will be required to purchase engines with on-board diagnostics, but engine manufacturers will be required to meet the certification requirements, including manuals for service personnel. They will also be required to provide the specifications equipment manufacturers must follow to install dashboard warning lights.