The US Environmental Protection Agency (EPA) has lifted requirements in the US to install diesel exhaust fluid (DEF) sensors in diesel engines. This measure is expected to save farmers $4.4 billion (€3.8 billion) annually in repair costs and downtime, according to the US Small Business Administration.

DEF, or Adblue as it is more commonly known, has been used within selective catalytic reduction (SCR) engine after-reatment systems as far back as 2010 to limit harmful engine emissions. The urea-based solution converts harmful nitrogen oxide (NOx) emissions into nitrogen and water.

Under the new guidance, manufacturers can now avoid DEF sensor failure on new and existing engines in the US by removing such sensors and replacing them with NOx sensors.

ADVERTISEMENT

The EPA outlined that users of diesel engines have been complaining about malfunctions with these after-treatment systems, causing unnecessary cost and downtime. Under new guidelines, vehicles receive a warning, but can continue to function as normal for longer periods of time before performance is affected.

In February, the EPA requested critical data on DEF system failures from the 14 manufacturers which account for over 80% of all products used in DEF systems. A preliminary review of the warranty data suggests that DEF sensor failures are a significant source of warranty claims.

US President Donald Trump announced the DEF sensor rollback at the recent White House Great American Celebration, where he said that his administration is “drastically limiting these ridiculous DEF rules, saving farmers and consumers billions”.

John Deere and AGCO were both present for Trump’s address and later released statements in support of the announcement.

Additionally, the EPA said that it will be issuing a new deregulatory proposal to completely remove all DEF de-ratements for new vehicles and engines.