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Cummins QSB DEF Doser Injector 2018-2021: OEM 5506856

CUMMINS QSB DEF DOSER INJECTOR 2018-2021: OEM 5506856

Shipping ICON

ORDERS PLACED BEFORE 3PM EST WILL SHIP SAME DAY

WARRANTY ICON

WARRANTY
1M MILES OR 1 YEAR

$895.00

CORE CHARGE:

$150.00
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 NUMBER5506856
PART TYPEDEF Doser Injector
BRANDTamerx Diesel Products
ENGINE MAKECummins
ENGINE TYPEQSB
YEAR2018-2021
PART NUMBER5506856TX
ADDITIONAL NOTES24 Volt

PRODUCT DESCRIPTION

This is a New, Tamerx DEF Doser Injector, Tamerx part number 5506856TX ( OEM Part Number 5506856 ).This part is primarily made for a Cummins QSB, production years 2018-2021, and comes with a One Million Miles or One Year Warranty. For additional warranty info Click Here

Additional Notes: 24 Volt

OEM NUMBERS

Primary OEM5506856
Additional OEM5506856

ADDITIONAL DETAILS

CONDITIONNew
UPC / Barcode
WEIGHT2.00 LBS

SHIPPING OPTIONS

Ship Weight : 2.00 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.


The OEM 5506856 DEF Doser Injector is designed for Cummins QSB engines from 2018 to 2021, delivering precise diesel exhaust fluid (DEF) injection into the aftertreatment system to support effective NOx reduction. Engineered to meet Cummins’ original equipment standards, this injector ensures proper atomization, accurate dosing, and reliable working conditions in SCR-equipped applications. It integrates directly with the vehicle’s emissions system, helping maintain compliance and reduce environmental impact across various off-highway and industrial equipment. Each unit is tested for spray pattern consistency, electrical function, and leak-free operation. A dependable replacement for maintaining optimal DEF system functionality in QSB engine platforms.

FITMENT CHART

YEARMAKEENGINE(S)
2018Cummins QSB
2019Cummins QSB
2020Cummins QSB
2021Cummins QSB

PEOPLE ALSO ASKS | BLOG(S)

The Cummins QSB engine platform, widely used in off-highway and industrial applications, employs advanced emissions systems to meet Tier 4 Final standards. A key part of this system is the DEF Doser Injector, responsible for injecting Diesel Exhaust Fluid (DEF) into the exhaust stream to support the Selective Catalytic Reduction (SCR) process. The correct OEM part for model years 2018 to 2021 is 5506856.

This injector ensures accurate DEF atomization, which is critical for effective NOx reduction and reliable system operation.

Core Features of the OEM 5506856 DEF Doser Injector:

  • Fine Mist Atomization Tip
    • Ensures efficient DEF distribution into the exhaust.
  • Heat-Resistant Body
    • Withstands high exhaust temperatures without warping.
  • Integrated Connector Port
    • Links with the DEF dosing module for precise control.
  • Sealing Surface and Mount Flange
    • Prevent leaks and ensure proper orientation.
  • Backflow Protection
    • Prevents exhaust gases from entering the DEF line.

This injector is specifically calibrated for the QSB platform’s flow rates and emissions strategy. Proper function depends on using clean DEF, routine system flushing, and correct torque during installation. Replacing the injector with OEM 5506856 helps maintain regulatory compliance and prevents SCR-related error codes or malfunctions.

The DEF (Diesel Exhaust Fluid) doser injector is responsible for spraying DEF into the exhaust stream to reduce harmful emissions. When it malfunctions, emissions control systems suffer, and your engine may respond with warnings or reduced drivability.

Here are the most common signs of a failing DEF doser injector:

  • Warning lights and fault codes
    • Check engine light or DEF system warnings
    • Diagnostic trouble codes (DTCs) like P204C, P207F, or P20E8
  • Increased DEF consumption or contamination
    • More frequent DEF refills than normal
    • Crystallized DEF buildup around the injector tip
    • Signs of DEF leaking near the exhaust pipe
  • Poor emissions system operation
    • Failed emissions test
    • Regeneration cycles not completing
    • SCR (Selective Catalytic Reduction) efficiency codes
  • Limp mode activation
    • The vehicle may limit speed or torque to meet emissions requirements
  • Unusual exhaust odors
    • Ammonia or sharp chemical smells may indicate incomplete DEF injection

If you notice any of these issues, a visual inspection and diagnostic scan are essential. A blocked, leaking, or electrically faulty doser injector can lead to bigger problems in the SCR system if ignored. Replacing the injector and ensuring clean DEF fluid can help restore system function.

Cleaning may help if buildup is minor, but replacement is often required if performance issues persist.

Yes, it contributes to the chemical reaction in the SCR system, which can alter temperature behavior.

It should be inspected during routine maintenance or when fault codes related to dosing appear.

It is mounted along the exhaust line just before the SCR catalyst.

Cummins DEF Doser Injectors

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