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Oshkosh Cummins DEF Head Unit

OSHKOSH CUMMINS DEF HEAD UNIT

Shipping ICON

ORDERS PLACED BEFORE 3PM EST WILL SHIP SAME DAY

WARRANTY ICON

WARRANTY
1M MILES OR 1 YEAR

$895.00

CORE CHARGE:

$250.00
iCORE DISCLAIMER: The CORE charge is a 30 day hold and will not be processed as long as the CORE is returned within 30 days. If you do not have a CORE or fail to return the CORE within 30 days, the CORE charge hold amount will be processed at that time.

AVAILABILITY IN STOCK
OEM NUMBER 3350441
PART TYPE DEF Head Unit
BRAND Tamerx Diesel Products
ENGINE MAKE Cummins
ENGINE TYPE
YEAR
PART NUMBER 4310-18-32
APPLICATION NOTES Oshkosh
ADDITIONAL NOTES DEF Header, 40 MICRON, 18"

PRODUCT DESCRIPTION

This is a Remanufactured, Tamerx DEF Head Unit, Tamerx part number 4310-18-32 ( OEM Part Number 3350441 ). This part is primarily made for a Cummins , and comes with a One Million Miles or One Year Warranty. For additional warranty info Click Here

Additional Notes: DEF Header, 40 MICRON, 18"

OEM NUMBERS

Primary OEM3350441
Additional OEM3350441

ADDITIONAL DETAILS

CONDITIONRemanufactured
UPC / Barcode00840490541443
WEIGHT8.00 LBS

SHIPPING OPTIONS

Ship Weight : 8.00 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.


Elevate your emissions control with the Oshkosh Cummins DEF Head Unit — precision-tuned for rugged reliability in extreme conditions. This high-accuracy module continuously monitors DEF level, temperature, and quality to help your SCR system stay optimized and prevent costly derates. Seamless integration, tough build, and dependable performance — it’s the upgrade your Oshkosh rig needs to stay clean, compliant, and ready for anything.

PEOPLE ALSO ASKS | BLOG(S)

When rugged off-road machines or specialty vehicles use a Cummins engine under heavy demands, one of the often underappreciated components in the emissions chain is the DEF (Diesel Exhaust Fluid) head unit. The Oshkosh Cummins DEF Head Unit, built to OEM 3350459 specifications, integrates multiple sensors and pathways to keep your DEF system honest. When it fails or falls out of calibration, you risk system faults, error codes, and potential engine derates—problems nobody wants in the field.

  • Combines multiple sensing functions—fluid level, temperature, and urea concentration—into one compact module

  • Manages precise dosing of DEF into the exhaust stream so the SCR system can effectively reduce NOx emissions

  • Built to OEM 3350459 tolerances, ensuring drop-in compatibility and proper calibration with Oshkosh / Cummins systems

  • Helps prevent emissions warning codes, system faults, and engine derates caused by sensor drift or failure

  • Designed with a 40-micron filter to protect downstream injectors and components from contamination

  • Engineered to endure harsh operational environments—vibration, temperature swings, and chemical exposure

  • Offered with a robust warranty (one million miles or one year) to back reliability

A failing DEF head unit often slips under the radar until it triggers a warning or diagnostic alert. By installing a properly matched, OEM-quality replacement, you restore the integrity of your emissions feedback loop, protect your engine’s aftertreatment system, and eliminate surprises on the job. For Oshkosh machines powered by Cummins, this module quietly ensures your emissions system stays clean, accurate, and dependable.

The DEF (Diesel Exhaust Fluid) head unit is a key part of modern diesel emissions systems, monitoring fluid level, quality, and temperature. When it fails or begins to degrade, the entire system can suffer, leading to fault codes, warnings, or even vehicle derates. Understanding what causes these failures can help operators take preventive steps and extend the life of this important component.

Common Causes of DEF Head Unit Failure or Degradation

  • Contaminated DEF Fluid
    Dirt, debris, or water in the DEF tank can damage sensors and cause inaccurate readings.

  • Crystallization Build-Up
    DEF naturally forms crystals when exposed to air. Over time, this buildup can coat sensors and interfere with proper function.

  • Extreme Temperatures
    Both freezing and excessive heat put strain on the head unit’s sensors and electronics, reducing their lifespan.

  • Electrical Issues
    Corroded, loose, or damaged connectors and wiring can disrupt communication with the engine control module (ECM).

  • Normal Wear and Tear
    Like all electronic components, sensors and circuits degrade with age and heavy use.

  • Improper Handling During Service
    Rough handling, skipped inspections, or use of improper tools during maintenance can damage the unit.

Most DEF head unit failures result from preventable issues such as contamination, crystallization, or electrical problems. By using high-quality DEF, protecting the system from extreme conditions, and following proper maintenance practices, operators can greatly reduce the risk of premature failure and keep their vehicles compliant and reliable.

Use a diagnostic scan tool to check real-time level and temperature readings and verify that no fault codes are active.

Erratic or missing sensor readings, DEF warnings, or engine derate are common symptoms.

It should be examined during the DEF system’s routine maintenance or whenever warning lights appear.

Flush or back-flush the fluid path with clean, compliant DEF, and inspect or replace the 40-micron strainer.

Cummins DEF Head Units

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