John Deere QLS Head Unit : OEM DZ128856
JOHN DEERE QLS HEAD UNIT : OEM DZ128856
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 DZ128856TX ( OEM Part Number DZ128856 ). 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 | DZ128856 |
| Additional OEM | DZ103806, DZ112747, DZ118298, DZ118673, DZ118674, DZ128856 |
ADDITIONAL DETAILS
| CONDITION | New |
| UPC / Barcode | 00840490542150 |
| 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.
Designed for reliability, the John Deere QLS Head Unit OEM DZ128856 ensures proper Diesel Exhaust Fluid (DEF) system function in John Deere machinery. This genuine OEM component is built to factory specifications, providing precise fitment and dependable operation across a range of agricultural and industrial equipment. By maintaining correct DEF flow and monitoring system performance, it helps support emissions compliance and consistent engine efficiency. Its durable construction is engineered to withstand demanding field and worksite conditions, offering long-lasting service life. For operators and fleet managers, this QLS head unit delivers OEM-backed quality and trusted reliability to keep John Deere equipment operating at its best.
PEOPLE ALSO ASKS | BLOG(S)
The John Deere QLS Head Unit OEM DZ128856 is a critical part of the Diesel Exhaust Fluid (DEF) system in modern John Deere equipment. Mounted on the DEF tank, it serves as both a monitoring and fluid management hub—ensuring the engine’s aftertreatment system operates cleanly and efficiently. Inside this advanced unit are several key components that work together to manage DEF flow, quality, and communication with the engine control module (ECM).
Main Components
- Header Housing
- The main body of the unit that mounts to the DEF tank, sealing the system and supporting all internal parts.
- Level Sensor
- Monitors the amount of DEF in the tank and sends this information to the ECM for accurate fluid level readings.
- Temperature Sensor
- Detects DEF temperature to prevent freezing or overheating and helps regulate system performance.
- Pickup Tube
- Draws DEF from the tank and delivers it to the dosing module for injection into the exhaust stream.
- Return Port
- Routes unused DEF back into the tank to maintain fluid circulation and system balance.
- Internal Filter
- Screens out impurities and crystals to protect sensitive downstream components.
- Electrical Connector
- Provides the interface for sensor data and power signals to communicate with the ECM.
- Seals and O-Rings
- Ensure the unit remains airtight and leak-free under varying temperatures and pressures.
The QLS Head Unit OEM DZ128856 is the control center of the DEF tank. By combining monitoring, filtration, and communication functions in one compact design, it helps John Deere engines stay efficient, compliant, and reliable in all working conditions.
The QLS Head Unit plays an essential role in your vehicle’s emissions and DEF (Diesel Exhaust Fluid) system. It monitors fluid level, quality, and temperature to ensure compliance and smooth operation. When it begins to fail, ignoring the problem can lead to system faults, derate mode, and costly downtime.
Common Signs of a Failing QLS Head Unit
Before it completely fails, you may notice:
- DEF or emissions fault codes appearing on the dashboard
- Incorrect DEF level readings (showing empty when full or vice versa)
- Check engine light tied to DEF or emissions errors
- Frequent derate countdowns, limiting vehicle speed or mileage
- Inconsistent or fluctuating sensor data
What to Do When the QLS Head Unit Starts Failing
- Do not ignore warning lights
- Continued driving can trigger full derate mode, restricting your speed to as low as 5 mph.
- Check for contamination
- Make sure the DEF tank and fluid are clean and free from debris or crystallization.
- Inspect wiring and connections
- Loose or corroded connectors can mimic head unit failure.
- Run a diagnostic scan
- Fault codes can confirm whether the QLS Head Unit or another component is causing the problem.
- Replace the unit if confirmed faulty
- QLS Head Units are sealed components and cannot be repaired or serviced. Replacement is the only reliable fix.
How to Prevent Future Failures
- Use only certified DEF fluid.
- Keep storage containers sealed and clean.
- Avoid exposing the DEF system to extreme heat or freezing conditions.
- Schedule regular inspections to catch issues early.
If your QLS Head Unit is failing, act quickly to avoid full derate and emissions compliance issues. Replacement with a proper OEM unit is the safest, most effective way to restore normal operation and keep your truck on the road.
It’s designed to precisely control and manage the fuel injection system in compatible John Deere engines.
Yes, it supports accurate fuel metering that contributes to efficient engine operation.
Yes, calibration may be necessary to align with your specific engine parameters.
Each unit is factory-tested to ensure it meets strict OEM quality and reliability standards.
John Deere QLS Head Units
