
Cummins L9 DOC Filter 2018-2021: OEM 4394859
CUMMINS L9 DOC FILTER 2018-2021: OEM 4394859

ORDERS PLACED BEFORE 3PM EST WILL SHIP SAME DAY

WARRANTY
1M MILES OR 1 YEAR
PRODUCT DESCRIPTION
This is a Remanufactured Tamerx DOC Filter, Tamerx part number 102-0154RM-DOC-15 ( OEM Part Number 4394859 ). All parts are proudly remanufactured in the U.S.A. to the highest of OEM standards, and improvements are often applied to the original design in the remanufacturing process. This part is primarily made for a Cummins L9, production years 2018-2021, and comes with a One Million Miles or One Year Warranty. For additional warranty info Click Here
Additional Notes: Inlet Catalyst
OEM NUMBERS
| Primary OEM | 4394859 |
| Additional OEM | 4394859 |
ADDITIONAL DETAILS
| CONDITION | Remanufactured |
| UPC / Barcode | 00840490549739 |
| WEIGHT | 35.00 LBS |
SHIPPING OPTIONS
Ship Weight : 35.00 LBS
UPS Ground, 2nd Day Air, Next Day Air
SHIPPING POLICY
Tamerx Diesel Products ships via UPS Ground. Next day air shipping can be arranged for a reasonable price of anywhere from $50.00 - $100.00 depending on the weight of the product and your location. We will do everything we can to make sure that you get the service you need. We understand how important it is to receive your order as quickly as possible.
In most cases Tamerx Diesel Products only needs one address, as long as your product is shipping to the same location as your billing information. In order to eliminate credit card fraud, your billing information must match the credit card you provide.
The terms, conditions, and details of our warranty vary from product to product. Specific warranty details can be found below.
Tamerx Diesel Products provides a replacement warranty on all of our parts. The duration and mileage limitations of the warranty vary by product and are specified on the product's detail page/item listing.
Please note that the warranty covers replacement of the part and the cost of shipping the replacement part to you only. It does not cover any shop, labor, towing, or any similar or related costs. This is not a "money back guarantee".
If you experience a problem with your part or it is not functioning properly, the correct warranty procedure is to call us at (510) 257-1777 (8:00 AM - 5:00 PM ET Monday through Friday). Be sure to have your order number and/or other relevant order information ready so we can easily locate your order and resolve your issue as quickly as possible. From that point, we will review with you any troubleshooting steps that may need to be taken and other areas or systems that can be checked to rule out external problems contributing to your part's issue. If a replacement is determined to be necessary, we will then arrange for your replacement part to ship out ASAP and issue any necessary return shipping labels and/or documents.
As is the case for the majority of the diesel products sold on Tamerx Diesel Products, your part's warranty is active as soon as you install it. In some other cases, warranty activation is contingent upon you sending us your core (i.e., your old part). Tamerx Diesel Products will provide you a return shipping label for parts that have a warranty with a core return condition. When we have received your core return, the part's warranty coverage begins. We reserve the right to void the product warranty if your core is not received within the allotted time, or if it isn't received at all. If the warranty for the diesel part you are purchasing has a core return requirement, it will be clearly noted on the product detail page/item listing.
What is a Core Charge?
A core charge (also called "core deposit") is similar to the deposit you might pay for a can or bottle of soda and is a standard requirement in the auto parts industry. For example, in many states, to promote recycling, you pay a deposit when you purchase a can of soda and receive your deposit back when you return the empty can. Many automotive parts have a core charge, or core price, that works in essentially the same way as a soda can deposit.
30 Day Core Charge Hold
You authorize Tamerx Diesel Products, to hold your credit card for the specified core charge amount and that you agree to return your core with 30 days of receiving the purchased part. When we have received your core return, the hold is released and the core charge payment is canceled.
The customer, or parts buyer, is responsible for any shipping costs associated with core returns unless otherwise specified in the product listing/detail page. Tamerx Diesel Products offers prepaid UPS shipping labels (SKU numbers UPS-CR1 and UPS-CR2) for use in returning your core that are available for purchase on our website during your shopping/order process.
The shipping label you will need to use for the core return is dependent upon what part you are purchasing. UPS-CR1 is good for cores weighing up to 20 pounds. UPS-CR2 is appropriate for shipping cores weighing 21 pounds or more. You must include enough information with the core return that clearly identifies it as a.) a Core Return, and b.) contains enough information we can use to clearly associate the core return with your order. Including a copy of the invoice or packing slip that came with the original shipment, clearly marked "Core Return", is ideal. Alternately, you can include a note marked as "Core Return" that includes your order number, full name and address, and phone number or other contact information. Failure to include this information with your returned core will most likely delay any due core credit being issued and/or delay any applicable warranty activation. Core returns need to be for the exact part purchased and cannot be damaged. Substituting another part in place of the part you have purchased is not acceptable.
All fluids must be drained.
If you have purchased a set or a parts package, you will need to return cores for all components of the set. For example, if you have purchaed a high pressure oil pump with an IPR valve, you will need to return both HPOP and IPR valve cores to receive proper credit. If you have purchased an EGR cooler/EGR valve package, your core return must consist of an EGR cooler core and an EGR valve core, or core credit will not be given.
Core Charges are often mandated by state legislature, and, as such, the actual core charge and taxes on the charge may vary depending on the state in which you buy your part. The Tamerx Diesel Products core charge presented to you online today with your item is representative of the most common core charge.
Covering 2018–2021 Cummins L9 engine applications, the OEM 4394859 DOC Filter is designed to maintain proper exhaust aftertreatment operation and ensure emissions compliance. This Diesel Oxidation Catalyst (DOC) plays a critical role in converting harmful exhaust gases into less harmful compounds before they continue through the DPF and SCR system. Manufactured to original equipment specifications, it provides accurate fitment and reliable compatibility with factory-installed sensors and mounting hardware. Its heavy-duty construction is built to withstand elevated exhaust temperatures and the demanding conditions of commercial truck use. As a direct OEM replacement, this Cummins L9 DOC Filter helps preserve aftertreatment system integrity while reducing the likelihood of unexpected downtime. Tamerx Diesel Products LLC offers dependable diesel emissions components that meet strict manufacturer standards for long-term reliability.
FITMENT CHART
| YEAR | MAKE | ENGINE(S) | ||||
|---|---|---|---|---|---|---|
| 2018 | Cummins | L9 | ||||
| 2019 | Cummins | L9 | ||||
| 2020 | Cummins | L9 | ||||
| 2021 | Cummins | L9 | ||||
PEOPLE ALSO ASKS | BLOG(S)
Serving as the first stage of emissions treatment, the Cummins L9 DOC Filter 2018–2021 (OEM 4394859) plays a central role in the engine’s aftertreatment system. As a Diesel Oxidation Catalyst (DOC), its main function is to reduce harmful exhaust gases immediately after they leave the engine.
The DOC initiates oxidation reactions that convert carbon monoxide and unburned hydrocarbons into less harmful compounds before the exhaust moves downstream to the Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR) components. By treating pollutants at the start of the process, it supports the overall efficiency and reliability of the entire emissions system.
Primary Role of OEM 4394859
- Converts carbon monoxide into carbon dioxide
- Breaks down unburned hydrocarbons
- Generates heat necessary for DPF regeneration
- Prepares exhaust gases for further treatment downstream
- Supports compliance with EPA emissions regulations
Because it operates at the front of the aftertreatment assembly, the DOC directly affects the performance of downstream components. A restricted or damaged unit can lead to system faults, reduced fuel efficiency, and increased downtime.
For 2018–2021 Cummins L9 engines, the OEM 4394859 DOC filter ensures proper integration with factory calibrations while maintaining consistent and reliable emissions control.
At the core of most DOC (Diesel Oxidation Catalyst) filter problems is contamination. When unwanted substances enter the exhaust stream, they coat the catalyst surface and prevent it from functioning properly. Over time, this buildup restricts airflow and can permanently damage the filter.
Contamination usually traces back to engine-related issues. If those concerns are not corrected quickly, the DOC can become clogged or overheated.
The most common causes of DOC filter failure include:
- Excessive soot from incomplete combustion
- Faulty fuel injectors allowing unburned fuel into the exhaust
- Oil entering the exhaust due to worn engine components
- Coolant leaks contaminating the catalyst material
- Poor fuel quality leaving heavy deposits
- Extended idling that prevents proper exhaust temperatures
Thermal stress is another contributing factor. Sudden or extreme temperature changes inside the exhaust system can crack or melt the internal catalyst structure.
Ignoring warning lights or delaying maintenance often allows minor problems to escalate. Identifying engine issues early, maintaining clean fuel and fluids, and following recommended service intervals are the most effective ways to prevent DOC filter failure and avoid costly repairs.
It may need replacement when exhaust restrictions or aftertreatment warnings indicate it is no longer effectively conditioning gases.
It is a diesel oxidation catalyst that helps manage exhaust gas constituents in the aftertreatment process.
Matching the part number on your current DOC filter to 4394859 confirms it is the correct component.
Yes, it functions together with components such as the diesel particulate filter and SCR system to help manage emissions.












