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If you’re looking, it’s not hard to find someone who’ll modify or remove the Diesel Exhaust Fluid (or DEF) emissions systems on your farm equipment. Given the open availability of this service, a farmer could be forgiven for believing that DEF modifications are legal.

They’re not. In the U.S., the EPA Clean Air Act prohibits anyone from tampering with an emission control device on a motor vehicle by removing it or making it inoperable. Canada has essentially the same law under a different name, the Canadian Environmental Protection Act.

DEF tampering is illegal, yet it happens. Why is this occurring and what are the possible consequences?

Kevin Rossler, Sales Manager for Markusson New Holland Ag near Regina, recalls that early DEF systems could be problematic.

“As it progressed into the Tier-Four emissions or DEF systems, there were early problems in agricultural equipment,” says Rossler. “An error code from a sensor failing at seeding time could shut you down, and that’s pretty frustrating. That caused some operators to want to get rid of the DEF systems, or get DEF delete kits to get away from using it.”

Tampering with a DEF system can put someone on the wrong side of the law, but that’s not the only risk involved. It also will void the equipment manufacturer’s warranty. When equipment with altered DEF comes to a dealership as a trade-in, it needs to have its original DEF settings restored, before it can be resold. In Rossler’s experience, that’s $5,000 to $7,000 right there.

He encourages equipment owners to get over any lingering misperceptions about DEF because current versions of this technology perform far more reliably. DEF systems are highly unlikely to cause problems in the field, but they’re great at what they were designed to do: control emissions from farm equipment and help maintain farming’s solid environmental credentials.

“There’s no comparison between early DEF systems and what we have today,” says Larry Hertz, WEDA’s Regional Vice-President for Canada. “Today, you could put your face next to the exhaust if you wanted to, and there’s nothing coming out. DEF is important for maintaining air quality, and it’s the law. All the more reason to leave your DEF intact and let it do its job.”