Release 04-32      

December 10, 2004


Jerry Martin
Gennet Paauwe
(916) 322-2990
ARB Enforces Software Regulation Upgrade for Big-Rig Trucks

-- The California Air Resources Board (ARB) has enacted a regulation that will require owners of nearly 60,000 heavy-duty trucks, school buses and diesel-powered motor homes built between 1993 and 1999 to have their computer software upgraded to reduce excess smog-forming emissions. The action was taken after a seven-month trial voluntary program was unsuccessful in upgrading enough trucks.

ARB Chairman, Dr. Alan Lloyd, said, “These vehicles have been operating on California’s streets and roads for more than ten years without any appreciable effort being made to replace their defective software and reduce their emissions. In March, we gave the manufacturers six months to upgrade a reasonable number of these trucks to avoid regulation but we have not seen enough progress to wait longer and put Californians at further risk, therefore we must enact the regulation without further delay.”

The regulation, adopted in March 2004 by the ARB will require most heavy-duty diesel trucks, buses and motor homes built between 1993 and 1999 to install new software, a process called reflash, to prevent the release of additional nitrogen oxide emissions. The ARB adopted the regulation after data showed that only about 13 percent of heavy-duty diesel vehicles that need reflash have been upgraded.

The upgrade requirement stems from a $1.04 billion settlement between U.S. EPA, ARB and the six largest truck manufacturers: Detroit Diesel Corp. (DDC), Renault/Mack, Volvo, International, Caterpillar and Cummins over emission control software that increased emissions when the vehicle operated under conditions not included in government emission compliance tests. As part of that settlement, manufacturers agreed to reflash their 1993 through 1998 vehicles during engine overhauls, projected to be at about 350,000 miles. However, most of these engines have long exceeded that mileage, some are now over one million miles old, without being overhauled. As a result, the ARB required the upgrades whether engines are being overhauled or not.

In March, the ARB gave manufacturers until November 2004 to voluntarily reflash 35 percent of all California registered vehicles that required the upgrade, from the 13 percent already upgraded. Only one manufacturer, DDC, was able to meet that goal. The other manufacturers fell short of the goal and overall achieved a voluntary rate of only 18 percent of all vehicles needing the upgrades despite a concerted effort by the California Trucking Assn. to conduct them throughout the summer. As a result of its effort, DDC was allowed to continue its voluntary compliance program.

The mandatory reflash program will require the oldest trucks (1993-94 models) to be upgraded by April 30, 2005. Those built in model years 1995-96 to have their upgrades completed by August 31, 2005, and those built in 1997 and 1998 must be reflashed by December 31, 2005. Owners of 1997 and 1998 medium heavy-duty vehicles, mainly delivery trucks and motor homes, have until December 31, 2006, to have the reflash completed.

The Air Resources Board is a department of the California Environmental Protection Agency. ARB's mission is to promote and protect public health, welfare, and ecological resources through effective reduction of air pollutants while recognizing and considering effects on the economy. The ARB oversees all air pollution control efforts in California to attain and maintain health based air quality standards.

The energy challenge facing California is real. Every Californian needs to take immediate action to reduce energy consumption. For a list of simple ways you can reduce demand and cut your energy cost, see our website at

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