Cummins B6.7, L9 DOC Filter 2018-2024: OEM 4394879

A Dependable DOC Solution for Cummins B6.7 & L9 Engines

What is it?
The Diesel Oxidation Catalyst (DOC) filter for Cummins B6.7 and L9 engines (model years 2018–2024), OEM reference 4394879, is a critical emissions-control component. It helps convert hydrocarbons (HC) and carbon monoxide (CO) in the exhaust stream into cleaner, less harmful gases, enabling the aftertreatment system to operate steadily and reliably.

Why choose this DOC Filter?
Engineered to fit original equipment specifications for both B6.7 and L9 platforms, this DOC filter ensures correct installation and dependable integration with the exhaust and aftertreatment system. A mismatched, worn, or blocked filter can lead to increased exhaust restriction, frequent regeneration events, or emissions-related fault codes. Choosing the correct DOC filter supports consistent exhaust flow and dependable emissions-system behavior.

Key Benefits
✅ Converts HC and CO into cleaner exhaust output
✅ Supports proper 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 conditions

Applications
Ideal for medium- and heavy-duty trucks, commercial vehicles, and equipment powered by Cummins B6.7 or L9 engines from 2018 through 2024. This DOC filter is particularly well-suited for fleet, vocational, and on-road applications where emissions compliance and reliable system performance are essential.

Installation Notes
Before servicing, ensure the exhaust and aftertreatment system has fully cooled. Remove the existing DOC filter and inspect adjacent exhaust piping, sensors, and hardware for soot buildup, cracks, or signs of wear. Install the replacement using new clamps, gaskets, and seals. After installation, clear any stored emissions-system fault codes and verify proper exhaust system behavior through diagnostic checks.

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