Diesel Exhaust Fluid

DEF is a commonly used acronym, it stands for Diesel exhaust fluid.

“Exhaust Fluid” sounds like a made-up term, like “Blinker fluid”, but it’s actually an essential fluid in most modern diesel engines.

DEF is a liquid used in diesel engines and vehicles equipped with selective catalytic reduction (SCR) systems. 

SCR systems are intended to help reduce emissions of nitrogen oxides (NOx) from diesel engine exhaust. 

In these systems DEF is injected into the diesel exhaust stream, where it reacts with NOx to and is converted into nitrogen and water, which are harmless. 

The precise amount of DEF that is injected, or dosed, is controlled by a vehicle’s computer system.

The computer ensures that the correct amount is used to suit the vehicle’s current driving conditions. This process is often referred to as “DEF dosing”.

What is a DEF Dosing Valve?

A DEF dosing valve is a component of a diesel engine, used in diesel vehicles which use selective catalytic reduction (SCR) systems. 

A DEF dosing valve controls the flow of diesel exhaust fluid (DEF) into the exhaust stream, which reduces an engine’s harmful nitrogen oxide (NOx) emissions.

A dosing valve is controlled by a diesel vehicle’s computer system, which calibrates the appropriate amount of DEF to inject, according to current driving conditions. 

A DEF dosing valve is an important component of the SCR system. 

A properly functioning DEF dosing valve is necessary to ensure that a diesel vehicle can pass an emissions test and meet emissions standards.