Freightliner Detroit DD5, DD8, DD13, DD15 DEF Head Unit
FREIGHTLINER DETROIT DD5, DD8, DD13, DD15 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 2327-20-4 ( OEM Part Number 04-33656-000 ).This part is primarily made for a Detroit DD5, DD8, DD13, DD15, production years 2021-2024, and comes with a One Million Miles or One Year Warranty. For additional warranty info Click Here
Additional Notes: DEF Header, Analog, SAE, Detroit, 20"
OEM NUMBERS
| Primary OEM | 04-33656-000 |
| Additional OEM | 04-33656-000 |
ADDITIONAL DETAILS
| CONDITION | Remanufactured |
| UPC / Barcode | 00840490541719 |
| 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.
Engineered for reliability, the Freightliner Detroit DD5, DD8, DD13, DD15 DEF Head Unit OEM 04-33656-000 supports proper Diesel Exhaust Fluid system function in model years 2021–2024. This genuine OEM component is manufactured to Detroit Diesel specifications, ensuring accurate fitment and dependable operation across a wide range of applications. By keeping the DEF system operating correctly, it helps maintain emissions compliance and steady engine performance. Its durable build is designed for the demanding conditions of commercial trucking, providing long-term service life. For operators and fleets, this DEF head unit offers OEM-certified quality and the assurance of consistent reliability.
FITMENT CHART
| YEAR | MAKE | ENGINE(S) | ||||
|---|---|---|---|---|---|---|
| 2021 | Detroit | DD5 | DD8 | DD13 | DD15 | |
| 2022 | Detroit | DD5 | DD8 | DD13 | DD15 | |
| 2023 | Detroit | DD5 | DD8 | DD13 | DD15 | |
| 2024 | Detroit | DD5 | DD8 | DD13 | DD15 | |
PEOPLE ALSO ASKS | BLOG(S)
From 2021 to 2024, Freightliner trucks powered by Detroit engines such as the DD5, DD8, DD13, and DD15 used the DEF Head Unit OEM 04-33656-000 as a critical part of their emissions system. This component, often called a DEF header, mounts at the top of the DEF tank and acts as the interface between the Diesel Exhaust Fluid and the vehicle’s electronic control system.
Core Functions
- DEF Level Monitoring
- Continuously measures how much DEF is in the tank and relays that information to the engine control module (ECM).
- Temperature Sensing
- Tracks DEF temperature to ensure it stays within safe operating ranges and to detect freeze conditions.
- Fluid Routing Hub
- Provides suction and return ports that move DEF between the tank and the dosing system while keeping the fluid flowing correctly.
- Internal Filtration
- Includes a fine filter or strainer to block particles and prevent crystallization from damaging the dosing system.
- Electrical Signal Output
- Sends sensor data as analog signals to the ECM, allowing accurate monitoring and control of the DEF system.
- No Internal Valve
- This unit is designed without a shutoff valve, focusing only on sensing, routing, and communication.
By combining monitoring, heating support, filtration, and fluid routing in one assembly, the DEF Head Unit OEM 04-33656-000 ensures reliable DEF supply and proper system operation. Without it, the truck’s emission system could not maintain compliance or protect itself from fluid-related faults.
Your DEF (Diesel Exhaust Fluid) head unit is a critical part of your vehicle’s emissions system. When it begins to fail, your truck will usually give clear signals that something is wrong. Recognizing these warning signs early can help you avoid being stranded in derate mode.
Common Warning Signs of a Bad DEF Head Unit
Watch for these symptoms that indicate the unit may be failing:
- DEF system fault codes
- displayed on the dashboard
- Check engine light
- triggered by emissions errors
- Inaccurate DEF readings,
- such as showing empty when the tank is full
- Premature derate countdowns,
- reducing mileage or operating time
- Vehicle entering limp mode,
- restricting speed to 5 mph or less
- Intermittent system warnings,
- with alerts that appear and disappear
The DEF head unit monitors fluid level, temperature, and quality. When sensors inside the unit stop working, the engine control module receives faulty data and responds by limiting your vehicle’s operation to remain compliant.
If you notice these warning signs, it’s best to schedule service right away. A failing DEF head unit cannot be repaired, and early replacement is the only way to prevent costly downtime.
It is a genuine OEM DEF head unit for Freightliner trucks with Detroit DD5, DD8, DD13, and DD15 engines from 2021–2024.
It tracks DEF tank fluid level, quality, and temperature to support emissions system operation.
A failing unit can trigger fault codes, DEF warnings, and potential derate conditions.
You can verify compatibility by checking OEM number 04-33656-000 against your truck’s service documentation.
Detroit DEF Head Units
