Cummins L9 SCR 2018-2021: OEM 5418542

Reliable NOx Reduction for Cummins L9 Engines (2018–2021)

What is it?
The Cummins L9 SCR (Selective Catalytic Reduction) assembly, designated by OEM part number 5418542, is an emissions aftertreatment component for Cummins L9 engines manufactured between 2018 and 2021. Working in tandem with Diesel Exhaust Fluid (DEF), this unit helps convert nitrogen oxides (NOx) in the exhaust into nitrogen and water before the gases exit the system, contributing to regulated emissions control.

Why choose this SCR Assembly?
This SCR module is engineered to Cummins’ original specifications for the L9 platform, ensuring the correct fit and seamless interface with DEF injection systems, sensors, and engine control modules. Over time, SCR performance can diminish due to normal wear or contamination, which can reduce NOx conversion efficiency and trigger emissions system alerts. Choosing the correct OEM-specified assembly supports more consistent emissions control and steady exhaust system behavior.

Key Benefits
✅ Designed for Cummins L9 emissions systems (2018–2021)
✅ Supports dependable NOx reduction with DEF interaction
✅ Helps maintain coordinated work with related aftertreatment components
✅ Direct-fit replacement — no modifications required
✅ Built to withstand demanding exhaust temperatures and duty cycles

Applications
This SCR assembly is suitable for medium- and heavy-duty vehicles equipped with Cummins L9 engines built between 2018 and 2021. It’s commonly used in delivery fleets, vocational trucks, regional transport rigs, and other commercial platforms where dependable emissions control and regulatory compliance are essential.

Installation Notes
Before servicing, allow the exhaust and aftertreatment system to cool completely. Remove the existing SCR module and inspect adjacent DEF lines, sensors, and mounting hardware for wear, soot buildup, or damage. Install the replacement SCR assembly with proper seals and fasteners to ensure a secure, leak-free fit. After installation, clear any stored system codes and verify correct SCR performance using diagnostic tools.

Final Thoughts
If your Cummins L9-equipped vehicle is showing NOx-related warnings, fluctuating emissions readings, or inconsistent exhaust behavior, replacing the SCR assembly with the correct OEM-specified part can help restore coordinated aftertreatment performance. The Cummins L9 SCR (OEM 5418542) plays a key role in managing regulated exhaust chemistry and supporting reliable operation across a variety of duty cycles.