General Information

WARNING: This page is about a different car, the 2018 Nissan Titan XD. However, it is still accessible from the selected car via links, so may be relevant.

The decomposition tube (2) is the section of exhaust pipe between the Diesel Particulate Filter (DPF) (1) the and Selective Catalytic Reduction (SCR) catalyst (3).
The decomposition tube is designed to help atomize and mix the Diesel Exhaust Fluid (DEF) being sprayed into the exhaust stream for complete mono-nitrogen oxides (NOx) conversion.
The DEF dosing valve (4) is mounted on the decomposition tube and is positioned to spray DEF into the exhaust stream.
The SCR catalyst (3) is where ammonia reacts with NOx and passes over the catalyst and converts NOx to nitrogen and water.

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