Freightliner Cummins ISL, ISX15 DEF Head Unit
FREIGHTLINER CUMMINS ISL, ISX15 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 2337-20-1 ( OEM Part Number 04-31677-001 ).This part is primarily made for a Cummins ISL, ISX15, production years 2014-2016, and comes with a One Million Miles or One Year Warranty. For additional warranty info Click Here
Additional Notes: DEF Header, CCV, Analog, SAE, Cummins, 20"
OEM NUMBERS
| Primary OEM | 04-31677-001 |
| Additional OEM | 04-30798-001, 04-31677-001 |
ADDITIONAL DETAILS
| CONDITION | Remanufactured |
| UPC / Barcode | 00840490541740 |
| 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.
The Freightliner Cummins ISL, ISX15 DEF Head Unit OEM 04-31677-001 is a factory-original part designed for model years 2014–2016. Built to Cummins and Freightliner specifications, this unit ensures the Diesel Exhaust Fluid system functions properly to support emissions compliance and dependable engine operation. Its precise fit and OEM-certified construction provide consistent performance in demanding commercial trucking applications. With rugged durability, it is engineered to handle the challenges of heavy-duty use and deliver long-term reliability. For operators and fleets, this DEF head unit offers the trusted assurance of OEM quality to keep vehicles running smoothly and in compliance with regulations.
FITMENT CHART
| YEAR | MAKE | ENGINE(S) | ||||
|---|---|---|---|---|---|---|
| 2014 | Cummins | ISL | ISX15 | |||
| 2015 | Cummins | ISL | ISX15 | |||
| 2016 | Cummins | ISL | ISX15 | |||
PEOPLE ALSO ASKS | BLOG(S)
The DEF Head Unit with part number 04-31677-001 is a “tank header” style unit designed for diesel trucks running Cummins ISL or ISX15 engines during the 2014–2016 period. Its job is to act as a central sensor and fluid routing node, enabling the Selective Catalytic Reduction (SCR) system to manage Diesel Exhaust Fluid (DEF) accurately and reliably.
Core Operation & Function
- Fluid Header / Routing
- The unit sits on top of a 13–23 gallon DEF tank and provides the pickup port (for drawing fluid) and return port (for returning unused fluid). It ensures a continuous, balanced DEF flow between the tank and the dosing system.
- Sensing and Measurement
- It measures the level of DEF in the tank and monitors the DEF temperature. These readings tell the engine control module (ECM) how much fluid is available and whether it’s within proper temperature range for injection.
- Analog Signal Output
- The 04-31677-001 version uses analog outputs (voltage / resistance changes) rather than digital or CAN signals. The analog signals carry data about fluid level and temperature to the ECM.
- Filtration & Protection
- Inside the header, there’s a filter or strainer that catches particulates or crystal formation before fluid is sent downstream, protecting the dosing and injection systems.
- Thermal Management
- While it may not contain active heating elements itself, the head unit is designed to work with the vehicle’s thermal system, ensuring the DEF remains usable in cold conditions.
- Fault Detection & Control Logic
- If sensors report conditions outside acceptable ranges (e.g. level too low, temperature too low or high), the ECM can trigger warnings, restrict operations, or enter safe modes to protect components and maintain emissions compliance.
The OEM 04-31677-001 DEF Head Unit is both a sensor hub and fluid router inside the DEF system. It monitors fluid level and temperature, routes DEF in and out of the tank, protects against contamination, and communicates analog data to the ECM so the SCR system knows how much and when to inject.
A DEF (Diesel Exhaust Fluid) head unit is a critical component in modern emissions systems. It measures fluid level, quality, and temperature to keep trucks compliant with regulations. But like any part, it has a limited lifespan.
Average Lifespan of a DEF Head Unit
Most DEF head units last 5 to 7 years under normal operating conditions. However, several factors can shorten or extend that timeframe depending on how the system is handled and maintained.
Factors That Impact Lifespan:
- Quality of DEF fluid
- Using only certified DEF prevents sensor damage
- Storage and handling
- Contaminated or dirty containers introduce debris
- Operating environment
- Extreme heat or freezing temperatures add stress
- Maintenance practices
- Regular inspections catch small issues early
- Duty cycle
- Heavy use and harsh conditions can shorten life expectancy
How to Maximize Longevity
You can extend the life of a DEF head unit by:
- Always using clean, certified DEF fluid
- Storing DEF in sealed, temperature-controlled containers
- Protecting the tank from extreme weather when possible
- Scheduling routine system inspections
A DEF head unit should last several years, but its actual lifespan depends on proper DEF handling, storage, and regular care. Preventive practices are the key to avoiding early failures.
Yes, failure may trigger derate conditions that restrict vehicle operation.
It supplies the ECM with DEF data that helps regulate aftertreatment performance.
Yes, inaccurate signals from the unit often cause DEF warnings on the dashboard.
Regularly using clean DEF fluid and keeping the tank free of contaminants reduces risk.
Cummins DEF Head Units
