Cummins B6.7, L9 DOC Filter 2018-2024: OEM 4394840

Consistent Exhaust Treatment 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), with OEM reference 4394840, is a critical emissions-control component. It converts hydrocarbons (HC) and carbon monoxide (CO) from the exhaust stream into cleaner, less harmful gases, supporting stable operation of the aftertreatment system.

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

Key Benefits
✅ Converts HC and CO into cleaner exhaust output
✅ Supports the 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 environments

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 especially suited for vocational, fleet, and on-road applications where emissions compliance and dependable system behavior are essential.

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

Final Thoughts
If your B6.7- or L9-equipped vehicle is showing signs of elevated exhaust restriction, frequent regenerations, or emissions-related alerts, replacing the DOC filter with the correct OEM-specified unit is a practical step toward restoring consistent, reliable exhaust flow. This component plays a key role in preserving the integrity of the emissions-control system and supporting steady, dependable operation.