DEF sensors no longer required on trucks, other diesel equipment: EPA

In February, the EPA requested data on DEF system failures from a group of large manufacturers of diesel-driven equipment, which included not only trucks but also agricultural machinery. In its Friday announcement of the DEF sensor suspension, the EPA said it had received data from 11 of the 14 manufacturers it had asked to provide that information. “In less than a month, EPA has turned around preliminary findings to issue (Friday’s) guidance,” the EPA said.

The EPA cited data from the Small Business Administration which said shutdowns caused by faulty DEF sensors were costing farmers $4.4 billion per year and $13.79 billion in total savings as a result of the sensor requirement.

“I have heard from truck drivers, farmers, and many others complaining about DEF and pleading for a fix in all 50 states I visited during my first year as EPA Administrator,” EPA Administrator Lee Zeldin said in the EPA’s prepared statement. “Americans are justified in being fed up with failing DEF system issues.”

That statement said “preliminary review of the warranty data suggests that DEF sensor failures are a significant source of warranty claims and DEF-related inducement.”

EPA said the sensors are more formally known as urea quality sensors. The new guidelines also said the sensors can be switched over to nitrous oxide (NOx) sensors.

Seeking to end ‘deratements’

In August, the EPA announced that it would ask engine manufacturers to update DEF software to avoid “deratements,” which are incidents when an engine dramatically slows due to DEF supplies running out or other readings from the DEF sensor. It also will require engine manufacturers, beginning with the 2027 model year, to take engineering steps that would stop those deratements when the vehicle runs out of DEF.

Before recent changes, if a sensor received a bad reading even if it was faulty, a driver could be stranded on the road, or in the case of agricultural equipment, out in the field. But with the changes from August, there is now a 650-mile or 10-hour window before the engines begin to slow. 

In its announcement Friday, the EPA laid out what the August changes would do to impact trucks and other diesel equipment. Beyond the 650 miles/10-hour window, “the engine will only mildly derate, allowing trucks to operate normally and without speed limits for up to 4,200 miles or two work weeks. Only after about four work weeks does the speed drop to 25 mph until repairs are made. Nonroad equipment has no impact for the first 36 hours before a slight torque reduction then takes effect. “

Farms expect to benefit

While the changes effect all diesel engines, the Trump administration’s statements about the DEF changes frequently mentioned the impact on agriculture. The EPA shift was announced in conjunction with the “Great American Agriculture Celebration.”

In a prepared statement in support of the EPA move, the American Trucking Associations said “(the agency’s) decision to provide manufacturers with flexibility to suspend these inducements—and eliminate problematic sensors altogether by monitoring a truck’s actual emissions—is a pragmatic solution that reflects how these systems perform in the real world. “

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