John Deere QLS Head Unit : OEM DZ128838
JOHN DEERE QLS HEAD UNIT : OEM DZ128838
ORDERS PLACED BEFORE 3PM EST WILL SHIP SAME DAY
WARRANTY
1M MILES OR 1 YEAR
PRODUCT DESCRIPTION
This is a New, Tamerx QLS Head Unit, Tamerx part number DZ128838TX ( OEM Part Number DZ128838 ). This part is primarily made for a John Deere , and comes with a One Million Miles or One Year Warranty. For additional warranty info Click Here
OEM NUMBERS
| Primary OEM | DZ128838 |
| Additional OEM | DZ118671, DZ128838, RM100351 |
ADDITIONAL DETAILS
| CONDITION | New |
| UPC / Barcode | 00840490542167 |
| WEIGHT | 5.00 LBS |
SHIPPING OPTIONS
Ship Weight : 5.00 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 John Deere equipment, the QLS Head Unit OEM DZ128838 ensures accurate Diesel Exhaust Fluid (DEF) system function and dependable emissions control. This genuine OEM component is built to precise factory specifications, providing perfect fitment and consistent performance across a range of agricultural and industrial machines. By maintaining proper DEF flow and monitoring, it helps keep engines efficient and compliant with emissions standards. Its rugged construction is made to handle tough worksite and field conditions, offering long-term durability. For operators and fleet managers, this QLS head unit delivers OEM-backed quality and the reliability expected from John Deere components.
PEOPLE ALSO ASKS | BLOG(S)
The John Deere QLS Head Unit (part number DZ128838) is mounted atop the DEF (Diesel Exhaust Fluid) tank and acts as the sensor and fluid interface for the emission system. It’s often called a “header” or “tank header assembly.” Its job is to monitor fluid, manage flow, and feed information to the engine’s control system.
Core Operation & Steps
- Fluid Sensing
- The unit includes a level sensor (float or probe) that continuously monitors how much DEF remains in the tank. When the level drops, it sends signals to the engine control module (ECM) or emission controller.
- Temperature Monitoring
- A temperature sensor built into or near the fluid measures DEF temperature. This protects the system from freezing or from fluid that’s too warm, which might degrade performance.
- Fluid Routing / Header Function
- The head unit provides ports or passages for drawing DEF (suction or pickup) into the dosing system. It may also include a return path so unused DEF can flow back into the tank, maintaining balanced circulation.
- Filtration / Protection
- Inside the head unit is a fine filter or strainer that catches particles, crystals, or contaminants before they reach the dosing or injection devices.
- Signal Communication
- The sensors (level, temperature, possibly others) send electrical signals via wiring to the ECM or DEF controller. The control system uses that data to determine when to inject DEF, when to regenerate the DPF, or to flag faults.
- Sealing & Integration
- The unit mounts to the tank with gaskets, seals, and fasteners so that everything remains fluid-tight and resistant to vibration, thermal expansion, and chemical exposure.
The DZ128838 QLS Head Unit is the “bridge” between the DEF tank and the engine’s emissions control system. It measures fluid level and temperature, filters the fluid path, routes DEF into the dosing system, and communicates fluid status to the control module so the engine can manage aftertreatment properly.
The QLS (Quality Level Sensor) Head Unit is a key component of the DEF (Diesel Exhaust Fluid) system. It measures DEF level, temperature, and quality, sending data to the vehicle’s emissions control system. Because it’s constantly exposed to DEF fluid and temperature changes, its lifespan depends heavily on maintenance and environmental conditions.
Average Lifespan of a QLS Head Unit
A QLS Head Unit typically lasts 5 to 7 years under normal operating conditions. In well-maintained systems, it may last even longer. However, exposure to contaminated DEF, extreme weather, or poor handling can significantly shorten its life.
Factors That Affect Longevity:
- DEF Quality
- Contaminated or expired DEF can damage internal sensors.
- Storage Conditions
- DEF exposed to heat or freezing can cause crystallization inside the unit.
- Handling Practices
- Dirty or unsealed containers allow debris into the tank.
- Operating Environment
- Heavy-duty cycles and extreme climates accelerate wear.
- Maintenance Habits
- Regular system inspections help prevent premature failure.
How to Extend Service Life
You can extend your QLS Head Unit’s lifespan by:
- Using only certified DEF fluid.
- Keeping DEF tanks and containers sealed and clean.
- Avoiding direct exposure to heat or freezing temperatures.
- Scheduling regular DEF system inspections.
Most QLS Head Units last 5 to 7 years, but their lifespan depends on proper DEF handling and maintenance. Consistent care and contamination prevention are the best ways to ensure long-lasting, trouble-free operation.
It regulates the timing and delivery of fuel to maintain accurate engine operation.
While possible, professional installation is advised to ensure proper calibration and engine synchronization.
Using the exact OEM part ensures accurate fuel system function and reliable engine operation.
Yes, installation guidance is typically provided, and professional installation is recommended.
John Deere QLS Head Units
