Navistar/International International N13 DEF Head Unit
NAVISTAR/INTERNATIONAL INTERNATIONAL N13 DEF HEAD UNIT
ORDERS PLACED BEFORE 3PM EST WILL SHIP SAME DAY
WARRANTY
1M MILES OR 1 YEAR
PRODUCT DESCRIPTION
This is a Remanufactured, Tamerx DEF Head Unit, Tamerx part number 2321-22-2 ( OEM Part Number 2523591C91 ).This part is primarily made for a International N13, production years 2017-2020, and comes with a One Million Miles or One Year Warranty. For additional warranty info Click Here
Additional Notes: QLS DEF Header
OEM NUMBERS
| Primary OEM | 2523591C91 |
| Additional OEM | 2510966C1, 2510966C3, 2515986C1, 2515987C1, 2517604C1, 2523591C91, 4086046C91, 4097728C91, 4140918C91, 4254210C91, 4352100C92 |
ADDITIONAL DETAILS
| CONDITION | Remanufactured |
| UPC / Barcode | 00840490541184 |
| WEIGHT | 8.00 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.
Step into precision control with the Navistar / International N13 DEF Head Unit — expertly engineered to support International’s N13 engines with seamless DEF level, temperature, and quality monitoring in real time. Built for rugged environments and tested for lasting performance, this robust unit helps your SCR system avoid engine derates while keeping your operation clean, compliant, and confident mile after mile.
FITMENT CHART
| YEAR | MAKE | ENGINE(S) | ||||
|---|---|---|---|---|---|---|
| 2017 | International | N13 | ||||
| 2018 | International | N13 | ||||
| 2019 | International | N13 | ||||
| 2020 | International | N13 | ||||
PEOPLE ALSO ASKS | BLOG(S)
For fleets running Navistar or International trucks with the N13 engine, emissions compliance isn’t optional—it’s a must. A core component in that system is the DEF (Diesel Exhaust Fluid) head unit, and for the N13 the correct match is OEM 2523591C91, often sold under part number 2321-22-2. When this head unit is functioning properly, your SCR (Selective Catalytic Reduction) system gets reliable feedback, helping avoid error codes, derates, and downtime.
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Monitors DEF fluid level, temperature, and urea concentration inside the tank and relays accurate data to the engine control module
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Controls precise dosing of urea into the exhaust so NOx is reduced correctly via the SCR system
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Spec’d to OEM 2523591C91 tolerances, ensuring a correct fit and calibration for International N13 setups
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Helps prevent emissions fault codes, warning lights, or engine derates due to sensor drift or failure
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Built to withstand vibration, thermal cycling, and exposure to DEF fluid’s corrosive properties
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Designed for efficient replacement, reducing downtime in the field
Many emissions issues trace back to a degraded or failing DEF head that can’t maintain accurate readings. Installing the correct OEM 2523591C91 / 2321-22-2 DEF head restores sensor accuracy, protects your diagnostics chain, and helps ensure your N13 remains emissions-compliant and reliable on the road.
The DEF (Diesel Exhaust Fluid) head unit is an essential part of your vehicle’s emissions system, responsible for monitoring fluid level, quality, and temperature. If it isn’t working correctly, it can trigger warning lights, diagnostic trouble codes (DTCs), or even cause the vehicle to enter derate mode. Testing the DEF head unit helps confirm whether it’s operating as intended or needs service.
Ways to Test a DEF Head Unit
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Check for Warning Lights
Look for DEF system alerts or a check engine light, which may signal inaccurate readings from the unit. -
Scan for Diagnostic Trouble Codes (DTCs)
Use a diagnostic tool to identify codes such as P203F (low DEF level), P205B (temperature sensor fault), or P207F (DEF quality issue). -
Verify DEF Gauge Accuracy
Compare the actual fluid level in the tank with what the dashboard gauge displays. Inconsistent readings may indicate a faulty sensor. -
Monitor DEF Quality Alerts
If the system flags poor-quality DEF despite using certified fluid, the quality sensor may be malfunctioning. -
Observe Temperature Readings
Ensure the DEF head unit reflects realistic temperature changes during hot or cold conditions. Abnormal values can signal failure. -
Inspect for Build-Up or Corrosion
Look for DEF crystallization, dirt, or corroded connectors that may interfere with accurate sensor readings.
Testing your DEF head unit involves both electronic checks and physical inspections. If errors, inaccurate readings, or persistent fault codes continue after testing, the unit may need replacement. Regular checks can help detect problems early, reduce downtime, and keep your vehicle emissions-compliant.
It uses internal sensors and valves to meter DEF precisely according to engine load and emissions demand.
Symptoms include DEF system error codes, reduced engine power, or a limp mode triggered by emissions noncompliance.
The vehicle may refuse to operate at full power or be forced into a reduced performance/emissions compliance mode.
Keeping the DEF fluid clean, ensuring no water contamination, flushing the system periodically, and avoiding freezing help prolong its life.
International DEF Head Units
