Cummins B6.7, L9 DOC Filter 2018-2021: OEM 4394883

Reliable Exhaust Treatment for Cummins B6.7 & L9 Engines (2018–2021)

What is it?
The Diesel Oxidation Catalyst (DOC) filter for Cummins B6.7 and L9 engines (model years 2018–2021), OEM reference 4394883, is a key emissions-control component. It converts hydrocarbons (HC) and carbon monoxide (CO) in the exhaust stream into cleaner, less harmful gases, helping the aftertreatment system maintain stable and dependable operation.

Why choose this DOC Filter?
Engineered to meet original equipment specifications for both B6.7 and L9 engine platforms, this DOC filter delivers precise fitment and reliable integration with the exhaust and aftertreatment system. A mismatched, worn, or blocked filter can contribute to increased exhaust restriction, frequent regeneration cycles, or emissions-related fault codes. Installing the correct DOC filter supports consistent exhaust flow and dependable aftertreatment performance.

Key Benefits
✅ Converts HC and CO into cleaner exhaust output
✅ Supports effective function of downstream aftertreatment components
✅ Helps maintain steady exhaust flow and reduce restriction
✅ Direct-fit design — no modifications required
✅ Built for heavy-duty, high-temperature operating environments

Applications
Suitable for medium- and heavy-duty trucks, commercial vehicles, and equipment powered by Cummins B6.7 or L9 engines from model years 2018 through 2021. This DOC filter is particularly well-suited for vocational, fleet, and on-road applications where emissions compliance and dependable exhaust system behavior are essential.

Installation Notes
Before servicing, make sure the exhaust and aftertreatment system has fully cooled. Remove the existing DOC filter and inspect the adjacent exhaust piping, sensors, and mounting hardware for soot buildup, cracks, or other damage. Install the replacement using fresh clamps, gaskets, and seals. After installation, clear any stored emissions-system fault codes and verify correct exhaust system behavior through diagnostic checks.

Final Thoughts
If your B6.7- or L9-equipped vehicle is experiencing elevated exhaust restriction, emissions warnings, or inconsistent aftertreatment behavior, replacing the DOC filter with the correct OEM-specified unit is a practical way to restore clean, dependable exhaust flow. This component plays a key role in maintaining emissions-control system integrity and supporting reliable operation.