Terex Cummins ISL DEF Head Unit
TEREX CUMMINS ISL 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 4310-18-18 ( OEM Part Number 37344 ). This part is primarily made for a Cummins ISL, and comes with a One Million Miles or One Year Warranty. For additional warranty info Click Here
Additional Notes: DEF Header, 40 MICRON, 18"
OEM NUMBERS
| Primary OEM | 37344 |
| Additional OEM | 37344, T168098 |
ADDITIONAL DETAILS
| CONDITION | Remanufactured |
| UPC / Barcode | 00840490540576 |
| 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.
Built for precision and reliability, the Terex Cummins ISL DEF Head Unit, OEM part number 37344, is designed to monitor and manage Diesel Exhaust Fluid (DEF) levels, temperature, and quality for accurate emissions control. Manufactured to OEM specifications, this DEF head unit ensures proper fitment, dependable performance, and seamless communication with the engine control system. Constructed from high-quality, corrosion- and chemical-resistant materials, it withstands harsh diesel operating conditions for long-lasting durability. Each unit is rigorously tested for sensor accuracy, electrical performance, and long-term reliability. Ideal for professional diesel technicians and fleet maintenance operations, this OEM DEF head unit supports efficient emissions management and dependable operation for Cummins ISL engines used in Terex equipment.
PEOPLE ALSO ASKS | BLOG(S)
The DEF (Diesel Exhaust Fluid) Head Unit with part number 37344 is a critical component used in Terex equipment powered by Cummins ISL engines. It is mounted on the DEF tank and functions as the central interface between the fluid reservoir and the engine’s after-treatment system.
What It Does
- Monitors DEF Level
- It senses how much DEF remains in the tank and relays that information to the vehicle’s engine control module (ECM) so the system knows when refilling is required.
- Tracks Fluid Temperature
- The head unit monitors the temperature of the DEF fluid. If the fluid is too cold (risking freezing) or too hot (risking degradation), the system can respond accordingly.
- Routes the Fluid
- It acts as a “header”, providing a pickup port for drawing DEF from the tank into the dosing/injection system, and often includes a return path for unused fluid back into the tank.
- Protects the System
- Built-in filtration helps block particles or crystallized deposits that could flow out of the tank and damage downstream components.
- Communicates Signals
- It sends sensor data (level, temperature, condition) to the ECM or emission controller, enabling accurate dosing, diagnostics, and system protection.
On Terex machines with Cummins ISL engines, the DEF Head Unit OEM 37344 is the pivotal link between the tank and the emissions system. Without it, the SCR (Selective Catalytic Reduction) system cannot reliably monitor the fluid status, cannot dose accurately, and may face fault codes or fail to meet emissions requirements.
The DEF (Diesel Exhaust Fluid) Head Unit is a vital component in your vehicle’s emissions system. It monitors DEF level, temperature, and quality — ensuring your engine runs efficiently and meets emissions standards. When it fails, your truck can enter derate mode, limiting power and performance. Understanding the causes of DEF Head Unit failure helps prevent costly downtime and repairs.
Common Causes of DEF Head Unit Failure
- DEF Contamination
- The most common cause of DEF Head Unit failure is contaminated DEF fluid. Dirt, fuel, oil, or other impurities introduced during refilling can damage sensitive sensors. Even a small amount of contamination can alter the chemical balance of DEF and cause the sensors to fail.
- Crystallization
- When DEF is exposed to air, heat, or freezing temperatures, it can form crystals inside the tank. These crystals coat sensors and block the pickup tube, leading to inaccurate readings or total sensor failure.
- Extreme Temperatures
- The DEF system is sensitive to temperature fluctuations. Freezing conditions can cause DEF to expand and crack internal components, while high heat can break down the fluid and shorten sensor lifespan.
- Moisture and Corrosion
- Moisture intrusion — often caused by damaged seals or vents — leads to corrosion in the Head Unit’s electrical connectors and sensors. Over time, this corrosion disrupts signal transmission between the DEF Head Unit and the engine control module (ECM).
- Poor Handling and Storage Practices
- Using unclean containers or tools for refilling introduces dirt or chemical contaminants into the DEF tank. DEF should always be stored in sealed, non-metallic containers away from direct sunlight and extreme temperatures.
- Normal Wear and Aging
- Even with proper care, the DEF Head Unit has a typical lifespan of 5 to 7 years. Prolonged exposure to DEF fluid and vibration will naturally wear out sensors and internal circuitry over time.
How to Prevent DEF Head Unit Failure
- Always use fresh, certified DEF fluid that meets ISO 22241 standards.
- Keep DEF storage sealed, clean, and temperature-controlled.
- Avoid cross-contamination by using equipment dedicated only to DEF.
- Inspect the DEF tank regularly for crystallization, leaks, or buildup.
- Address warning lights or fault codes as soon as they appear.
A DEF Head Unit can fail due to contamination, crystallization, temperature extremes, corrosion, or natural wear. The best way to avoid failure is through proper DEF handling, storage, and regular maintenance — ensuring reliable operation and reduced downtime for your vehicle.
It manages the dosing of Diesel Exhaust Fluid (DEF) and monitors fluid level, temperature and pressure in the SCR system for the ISL engine.
Symptoms include SCR system fault codes, DEF dosing warnings, engine derate or “check emissions system” dashboard lights.
Because the correct unit ensures compatibility with calibration, wiring harness, fluid passages and data signals for the ISL engine/SCR system.
Relieve system pressure, drain or secure DEF lines, clean tank/flange surfaces, verify wiring harness and connectors are undamaged.
Cummins DEF Head Units
