Freightliner Cummins ISB 6.7L, ISL, L9 DEF Head Unit
FREIGHTLINER CUMMINS ISB 6.7L, ISL, L9 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 2324-18-2 ( OEM Part Number 04-35649-002 ).This part is primarily made for a Cummins ISB 6.7L, ISL, L9, production years 2018-2021, and comes with a One Million Miles or One Year Warranty. For additional warranty info Click Here
Additional Notes: DEF Header, Conc, 6-Bolt, Cummins, 18"
OEM NUMBERS
| Primary OEM | 04-35649-002 |
| Additional OEM | 04-31354-000, 04-31354-001, 04-31354-002, 04-31354-003, 04-31354-004, 04-35649-002 |
ADDITIONAL DETAILS
| CONDITION | Remanufactured |
| UPC / Barcode | 00840490541634 |
| 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.
Crafted to factory standards, the Freightliner Cummins ISB 6.7L, ISL, L9 DEF Head Unit OEM 04-35649-002 provides dependable operation for model years 2018–2021. This OEM component plays a key role in the Diesel Exhaust Fluid system, supporting emissions compliance and reliable engine performance. Designed for precision fit, it installs seamlessly and delivers consistent results in demanding trucking applications. Its rugged construction allows it to withstand the challenges of heavy-duty use while maintaining long-term service life. For operators who rely on Freightliner vehicles, this DEF head unit offers the trusted reliability of a genuine OEM replacement.
FITMENT CHART
| YEAR | MAKE | ENGINE(S) | ||||
|---|---|---|---|---|---|---|
| 2018 | Cummins | ISB 6.7L | ISL | L9 | ||
| 2019 | Cummins | ISB 6.7L | ISL | L9 | ||
| 2020 | Cummins | ISB 6.7L | ISL | L9 | ||
| 2021 | Cummins | ISB 6.7L | ISL | L9 | ||
PEOPLE ALSO ASKS | BLOG(S)
In Freightliner trucks powered by Cummins ISB 6.7L, ISL, or L9 engines (2018–2021), the DEF Head Unit (part number 04-35649-002) acts as a central sensor and fluid management module within the SCR (Selective Catalytic Reduction) emission control system. Its job is to monitor, regulate, and communicate essential information about the Diesel Exhaust Fluid (DEF) system so the engine’s control system can maintain clean exhaust.
Core Roles & Functions
- DEF Level Monitoring
- The head unit senses how much DEF fluid remains in the tank. This helps avoid running out unexpectedly, and feeds that data to the engine control module so warnings or alerts can be issued.
- Fluid Quality / Concentration Sensing
- It checks whether the DEF solution meets the correct chemical concentration (urea content and purity). If the solution is contaminated or off spec, the system can detect the problem.
- Temperature Sensing & Heating / Warmth Management
- Because DEF can freeze or become less effective at low temperatures, the head unit includes temperature sensors and may interface with heating circuits. This ensures fluid stays usable under cold ambient conditions.
- Fluid Flow / Header / Distribution Management
- The head unit is part of the header assembly (6-bolt design) that manages fluid pathways into the dosing/injection side, and sometimes return paths. It helps control how DEF is delivered into the exhaust aftertreatment system.
- Signal / Communication Interface
- All sensor readings—level, quality, temperature—are relayed to the engine’s electronic control module (ECM). The ECM uses that data to determine how much DEF to inject, detect faults, or trigger warnings.
Without a properly functioning DEF Head Unit, the SCR system can’t reliably meter DEF, detect bad fluid, or protect itself from freezing. Faults in the unit can lead to warning lights, emission noncompliance, or system derate as the control module protects the engine and emissions components. When maintained correctly, the OEM 04-35649-002 head unit is a critical part of ensuring the truck remains emission-friendly and dependable on the road.
The DEF (Diesel Exhaust Fluid) head unit is a small but critical part of a truck’s emission system. It monitors DEF level, temperature, and quality to keep vehicles compliant with emissions standards. When it fails, drivers often face warning lights, fault codes, and derate mode. But what actually causes these failures?
The Leading Causes of DEF Head Unit Failure
Several factors can shorten the life of a DEF head unit:
- Contamination
- Dirt, dust, or debris entering the DEF tank during refills
- Poor DEF handling
- Using containers not designed for DEF storage
- Extreme temperatures
- Heat or freezing can cause crystallization and sensor damage
- Fluid quality issues
- Using expired or uncertified DEF fluid
- Moisture intrusion
- Water or condensation interfering with sensitive electronics
- Normal wear
- Over time, components simply break down after years of service
Most causes of DEF head unit failure trace back to handling and storage. To extend its lifespan, always use certified DEF, store it properly, and inspect the system regularly. Preventing contamination is the single most effective way to avoid costly breakdowns.
It is an OEM DEF head unit designed for Freightliner vehicles with Cummins ISB 6.7L, ISL, and L9 engines from 2018–2021.
It monitors DEF fluid level, temperature, and quality inside the DEF tank assembly.
A failing unit can cause DEF system warnings, inaccurate readings, and restricted operation.
You should confirm fitment by verifying OEM part number 04-35649-002 with your Freightliner specifications.
Cummins DEF Head Units
