Cummins L9 SCR 2018-2021: OEM 5418684

Dependable NOx Control for Cummins L9 Engines (2018–2021)

What is it?
The Cummins L9 SCR (Selective Catalytic Reduction) assembly with OEM part number 5418684 is an emissions aftertreatment component engineered for Cummins L9 diesel engines built between 2018 and 2021. Functioning as part of the SCR system, it works with Diesel Exhaust Fluid (DEF) to help convert nitrogen oxides (NOx) in the exhaust into nitrogen and water before the gases exit the system, supporting emissions compliance.

Why choose this SCR Assembly?
This SCR module is built to meet Cummins’ original specifications for the L9 platform, ensuring proper fitment and dependable interaction with DEF dosing systems, exhaust sensors, and engine control electronics. Over time, SCR components can lose effectiveness due to use or contamination, which can reduce NOx conversion efficiency and trigger emissions alerts or uneven aftertreatment performance. Installing the correct OEM-specified unit helps maintain steadier exhaust behavior and coordinated emissions system operation.

Key Benefits
✅ Designed specifically for Cummins L9 aftertreatment systems (2018–2021)
✅ Supports reliable NOx conversion through DEF interaction
✅ Helps maintain coordinated operation with related emissions parts
✅ Direct-fit replacement — no modifications required
✅ Built to cope with demanding exhaust environments

Applications
This SCR assembly is suited for medium- and heavy-duty trucks and commercial vehicles powered by Cummins L9 engines manufactured between 2018 and 2021. It is commonly found in delivery fleets, vocational trucks, regional transport rigs, and other commercial platforms where consistent emissions control and regulatory compliance are essential.

Installation Notes
Before servicing, make sure the exhaust and aftertreatment system has cooled completely. Remove the existing SCR module and inspect nearby DEF lines, sensors, and mounting hardware for signs of soot buildup, wear, or damage. Install the replacement assembly using the correct seals and fasteners to achieve a secure, leak-free fit. After installation, clear any stored system codes and verify correct SCR operation using diagnostic tools.

Final Thoughts
If your Cummins L9-equipped vehicle is experiencing NOx-related alerts, fluctuating emissions readings, or inconsistent aftertreatment behavior, replacing the SCR module with the correct OEM-specified part can help restore balanced exhaust treatment and smoother overall system performance. The Cummins L9 SCR (OEM 5418684) plays a key role in managing regulated exhaust chemistry and supporting dependable vehicle operation.