WASHINGTON -- The U.S. Environmental Protection Agency has issued final rules requiring onboard diagnostic systems for over-the-road trucks and buses to monitor emission control systems.

Onboard diagnostic system have been required on passenger cars since the mid-1990s to monitor emission control systems and detect malfunctions.

The system alerts the driver of the problem, enabling a service technician to diagnose and repair the problem.

Now, they will be required on 2010 and later heavy-duty engines used in on-highway applications of vehicles weighing more than 14,000 pounds.

In addition to these requirements, EPA is requiring manufacturers to make available to the service and repair industry information necessary to perform repair and maintenance service on onboard diagnostic systems and other emissions-related engine components.

Under the new rule, manufacturers must install onboard diagnostic systems that monitor the functioning of emission control components and alert the vehicle operator to any detected need for emissions-related repair.

In addition, when a malfunction occurs, diagnostic information must be stored in the engine's computer to assist in diagnosis and repair of the malfunction.

After-treatment devices for example, the diesel particulate filters and oxides of nitrogen reducing catalysts - that will be used on diesel engines to comply with the 2010 emissions standards must also be monitored and their failure detected and noted to the driver.

There is a phase-in aspect to the regulation.

EPA is requiring that one engine family per manufacturer be certified to the onboard diagnostic system requirements in the 2010 through 2012 model years.

Beginning in 2013, all highway engines for all manufacturers will have to be certified to the new requirements.

The final rule is a major step in EPA's efforts to work with the California Air Resources Board to develop a consistent national heavy-duty onboard diagnostic systems program. EPA's new program is consistent with the California program in almost all important aspects, according to the agency.