EPA Eases DEF Systems Requirements

LINCOLN, Neb. (DTN) -- The Trump administration announced new guidance on Tuesday that allows farmers and truckers to revise software to prevent sudden speed and power losses caused by diesel exhaust fluid systems, or DEF.

Starting with model year 2027, U.S. Environmental Protection Agency guidance requires all new diesel on-road trucks to be engineered to avoid sudden and severe power loss after running out of DEF.

To fix the problem for vehicles already in use, EPA's new guidance allows software changes to be made on the existing fleet.

"In addition to providing certainty to manufacturers about how EPA wants this issue resolved, the agency is not requiring separate approvals beyond that provided in EPA's guidance," the agency said in a news release.

"This ensures that bureaucratic steps do not delay manufacturers' ability to put solutions into the field."

When DEF runs out or a system sensor fails, current systems can force a vehicle to drastically reduce speed or become inoperable.

In many cases, vehicles are limited to as little as five miles per hour within hours of a DEF-related fault, which causes disruptions in logistics, agriculture and construction.

Under the current regulations, when SCR technology sensors fail, vehicle operators have just four hours before a diesel engine becomes barely operable with speeds reduced to 5 miles per hour before shutting down.

With the new guidance for heavy-duty trucks, after a fault is detected only a warning light will appear for 650 miles or 10 hours. In addition, EPA said there would be no effect on vehicle performance for at least one day.

When that happens, EPA said the new guidance would lead to a derate of the engine by about 15% without limiting speed. This would allow trucks to operate normally for up to 4,200 miles or two additional work weeks. Speed would drop to 25 miles per hour after about four weeks of operating.

"Although this derate strategy was intended to ensure compliance with EPA's Tier 4 emissions standards, it has caused needless frustration, operational delays and real economic hardship for countless farmers, truckers and equipment operators," EPA said on Tuesday.

Since 2010, most on-road diesel trucks and many types of non-road equipment such as tractors and construction machinery have used selective catalytic reduction systems that inject DEF into exhaust streams to reduce nitrous oxide emissions.

"We have heard loud and clear from small businesses across the United States that the current DEF derates are unacceptable," EPA Administrator Lee Zeldin said in a statement.

"It is unacceptable that farmers, truckers, construction workers and many other small businesses continually experience failures of diesel-powered equipment when they need it most -- costing millions of dollars in lost productivity."

U.S. Secretary of Agriculture Brooke Rollins said the change in DEF guidance addresses a government regulation that ties the hands of farmers and ranchers.

"This commonsense reform will allow our agricultural producers to spend more time in the fields than in the repair shop," Rollins said in a statement.

Todd Neeley can be reached at todd.neeley@dtn.com

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