
Cummins DEF Head Unit : OEM ASP-908-2321-449
CUMMINS DEF HEAD UNIT : OEM ASP-908-2321-449

ORDERS PLACED BEFORE 3PM EST WILL SHIP SAME DAY

WARRANTY
1M MILES OR 1 YEAR
PRODUCT DESCRIPTION
This is a New, DuraWRX DEF Head Unit, DuraWRX part number ASP-908-2321-449 ( OEM Part Number ASP-908-2321-449 ). 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, 449mm
OEM NUMBERS
| Primary OEM | ASP-908-2321-449 |
| Additional OEM | 2512843C2, 2515988C3, 2523590C91, 4086806C91, 4087160C91, 4097724C91, 4097725C91, 4163693C91, 4163694C91, 4254215C91, 4353004C92, 601968, 602065, A000P868, ASP-908-2321-449 |
ADDITIONAL DETAILS
| CONDITION | New |
| UPC / Barcode | 00840490537149 |
| WEIGHT | 4.00 LBS |
SHIPPING OPTIONS
Ship Weight : 4.00 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.
Serving as a central component within Cummins SCR aftertreatment systems, OEM ASP-908-2321-449 is a DEF head unit designed to manage and distribute Diesel Exhaust Fluid throughout the dosing assembly. This unit is manufactured to OEM specifications to ensure proper fitment and compatibility with factory-installed exhaust and DEF system components. Built from durable materials, it is engineered to withstand the operating conditions common in modern diesel applications. The head unit supports accurate DEF flow control and system communication to maintain effective emissions treatment. It is a reliable solution for fleet maintenance and targeted repair needs requiring dependable aftertreatment system operation.
PEOPLE ALSO ASKS | BLOG(S)
The Cummins DEF Head Unit: OEM ASP-908-2321-449 is a multi-function module mounted on top of the Diesel Exhaust Fluid (DEF) tank. It integrates several sensing and supply components into one assembly to support proper SCR (Selective Catalytic Reduction) system operation.
Although serviced as a complete unit, the DEF head assembly contains several internal components that work together to monitor fluid condition and manage DEF delivery.
Key components of OEM ASP-908-2321-449 include:
- DEF Level Sensor
- Measures the amount of DEF remaining in the tank and sends that information to the engine control module (ECM).
- DEF Temperature Sensor
- Monitors fluid temperature to detect freezing or overheating conditions.
- DEF Quality Sensor (where equipped)
- Measures urea concentration to ensure proper DEF mixture.
- Supply Tube / Pickup Tube
- Draws DEF from the tank and routes it to the dosing pump or injector.
- Integrated Heater Element
- Prevents DEF from freezing in cold environments.
- Electrical Connector
- Connects the head unit to the vehicle wiring harness for communication with the ECM.
- Sealing Gasket and Mounting Flange
- Secures the unit to the DEF tank and prevents leaks or contamination.
Together, these components allow OEM ASP-908-2321-449 to provide accurate fluid monitoring and consistent DEF supply, which is essential for maintaining emissions compliance and proper SCR system performance.
The main cause of DEF head unit failure is internal sensor degradation caused by DEF contamination and crystallization. The DEF head unit contains the level, temperature, and quality sensors, all of which are constantly exposed to Diesel Exhaust Fluid. When DEF becomes contaminated or begins to crystallize, it can damage the internal sensing elements and electronics.
Crystallization commonly occurs when low-quality DEF is used, when the tank is exposed to excessive heat, or when contamination is introduced during filling. Over time, urea deposits can coat sensor surfaces, causing inaccurate readings or complete signal loss.
Midway through diagnosis, the most common contributing factors to DEF head unit failure include:
- Use of non-ISO 22241 compliant DEF
- DEF contamination with dirt, fuel, or coolant
- Crystallization buildup inside the tank
- Corroded electrical connectors or wiring
- Voltage irregularities or poor ground connections
- Prolonged exposure to extreme temperature cycles
In many cases, the head unit itself is not defective by design. Poor DEF handling practices, tank contamination, or electrical issues lead to premature failure.
Maintaining clean DEF, using proper storage practices, inspecting wiring connections, and addressing SCR system issues early are the most effective ways to prevent DEF head unit failure and ensure accurate system monitoring.
It connects the DEF pump, filter, and lines to the dosing injector for controlled delivery into the exhaust.
Yes, it is an OEM-specified component designed for direct replacement on compatible DEF systems.
Yes, issues with the head unit can cause emissions-related diagnostic trouble codes.
Yes, it works with DEF system sensors and the engine control module to help regulate fluid delivery.














































































