MCNEILUS Cummins DEF Head Unit
MCNEILUS CUMMINS 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 5410-18-FA01-11 ( OEM Part Number 1604691 ). This part is primarily made for a Cummins, 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 | 1604691 |
| Additional OEM | 1604691 |
ADDITIONAL DETAILS
| CONDITION | Remanufactured |
| UPC / Barcode | 00840490540286 |
| 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.
Dependable DEF system monitoring is delivered by the McNeilus Cummins DEF Head Unit: OEM 1604691, a direct-fit component for compatible McNeilus vehicles and equipment. Built to OEM specifications, this unit measures diesel exhaust fluid level, temperature, and quality to support emissions compliance and consistent aftertreatment performance. Its rugged construction ensures reliable operation in demanding work environments, helping protect both the exhaust system and overall engine efficiency. Choosing an OEM DEF head unit minimizes compatibility concerns and supports long-term reliability. This component is a proven solution for keeping McNeilus Cummins-powered equipment running smoothly and without interruption.
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The DEF (Diesel Exhaust Fluid) Head Unit with OEM part number 1604691 is a multifunction module used on McNeilus trucks or equipment powered by Cummins ISL engines. It’s mounted on top of the DEF tank and combines sensor, fluid‑handling, and monitoring functions into a single assembly. Typically remanufactured, this unit is built to match Cummins OEM specifications, and often comes with parts like a 40‑micron internal filter, heavy‑duty header connections, and a warranty (for instance, one year or one million miles depending on vendor).
The OEM 1604691 DEF Head Unit performs several crucial tasks:
- Monitors Fluid Level
- It senses how much DEF fluid remains in the tank, sending feedback to the vehicle’s engine control module so you know when refill is required.
- Monitors Temperature
- Since DEF can freeze or crystalize in cold conditions, this unit senses fluid temperature. If the fluid is too cold, it alerts the system so heating or protective functions can activate.
- Filters the DEF Fluid
- Internal screening (about 40 microns) removes particulates, debris, or contaminants before the fluid is used in the dosing system, protecting sensitive downstream parts.
- Manages Fluid Flow
- It handles the suction (pull from tank to dosing module) and return of excess or unused DEF fluid, ensuring proper fluid delivery and preventing air locks or flow interruptions.
A well‑functioning OEM 1604691 head unit ensures your emissions control system works correctly. If it fails or degrades:
- You might get warning codes or engine derates
- DEF may be unevenly dosed or the system may reject it
- Downstream components (like SCR catalyst or DEF injectors) can suffer from contamination
- Emissions may increase, and you could go out of compliance
Maintaining or replacing this head unit with suitable OEM or remanufactured units keeps your Cummins ISL engine clean, reliable, and compliant, reducing downtime and repair costs.
The DEF (Diesel Exhaust Fluid) head unit is a key part of your emissions system. It monitors DEF level, temperature, and fluid quality. When it starts to fail, it can trigger false warnings, cause unnecessary derates, or prevent the system from working properly.
How to Diagnose a Bad DEF Head Unit
To confirm whether the head unit is the issue, follow these steps:
- Run a scan tool
- Check for active or stored fault codes related to DEF level, quality, or temperature (common codes: SPN 1761, 3031, P203F).
- Inspect the fluid level manually
- Open the DEF tank and visually confirm the fluid level. If the dash reading is incorrect, the sensor may be faulty.
- Check wiring and connectors
- Look for signs of corrosion, broken pins, or damaged harnesses connected to the DEF tank.
- Review freeze/thaw history
- Crystallized DEF or frequent freeze cycles can damage internal sensors or heating elements.
- Monitor consumption
- A sudden increase or decrease in DEF usage may indicate inaccurate readings.
If these checks confirm signal errors and wiring is intact, the DEF head unit may need to be replaced.
Fault codes, false DEF readings, or engine derates are signs of a failing unit.
Yes, a bad unit can lead to reduced power, downtime, or failed inspections.
Yes, in some cases it may trigger derates or force the truck into limp mode.
Prolonged use may result in failed emissions tests and unplanned downtime.