Cummins L9 SCR 2018-2021: OEM 5505662

Purpose-Built NOx Management for Cummins L9 Engines (2018–2021)

What is it?
The Cummins L9 SCR (Selective Catalytic Reduction) assembly with OEM part number 5505662 is a key part of the emissions aftertreatment system for Cummins L9 diesel engines produced from 2018 through 2021. It works in tandem with Diesel Exhaust Fluid (DEF) to support a chemical reaction that converts nitrogen oxides (NOx) in exhaust gases into nitrogen and water before they exit the system, helping the vehicle meet regulated emissions standards.

Why choose this SCR Assembly?
This SCR module is built to match Cummins’ original design specifications for the L9 platform, offering precise fitment and reliable communication with DEF dosing equipment, emissions sensors, and engine control systems. Over time, SCR components can become less effective due to wear, contamination, or prolonged use, which may reduce NOx conversion efficiency and trigger emissions alerts. Selecting the correct OEM-specified assembly helps sustain consistent performance and smoother aftertreatment coordination.

Key Benefits
✅ Made specifically for Cummins L9 aftertreatment systems (2018–2021)
✅ Supports consistent NOx conversion with DEF interaction
✅ Helps maintain coordinated operation with other emissions components
✅ Direct-fit replacement — no alterations required
✅ Engineered for heavy-duty exhaust environments

Applications
This SCR assembly is suitable for medium- and heavy-duty trucks and commercial equipment equipped with Cummins L9 engines manufactured between 2018 and 2021. Typical uses include delivery fleets, vocational trucks, regional transport rigs, and other work vehicles where regulated emissions control is a core operational requirement.

Installation Notes
Before servicing, ensure the exhaust and aftertreatment system has fully cooled. Remove the existing SCR unit and inspect surrounding DEF lines, sensors, and mounting hardware for signs of wear, soot buildup, or damage. Install the replacement SCR assembly using the proper seals and fasteners to secure a tight, leak-free fit. After installation, clear any stored fault codes and verify correct aftertreatment behavior 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 unit can help restore balanced exhaust treatment and dependable system performance. The Cummins L9 SCR (OEM 5505662) plays an essential role in managing regulated exhaust chemistry and supporting reliable vehicle operation across varied duty cycles.