DEF

Genuine OEM DEF Parts: Sensors, Multifunction Head Units & Doser Injectors

A flashing derate warning or a DEF fault code can shut your truck down in minutes — and every hour it sits is an hour it’s not earning. Most DEF system failures trace back to one of a handful of components: a worn level sensor, a cracked multifunction head unit, or a failing doser injector. Replacing it with the wrong part, or a cheap aftermarket substitute, often just brings the same fault code back a few weeks later. That’s why every DEF part in this catalog is genuine OEM, sourced directly against the manufacturer’s original part number.

What's in this category

This collection covers the core components of the Diesel Exhaust Fluid (SCR) system across heavy trucks, buses, and off-road equipment:

• DEF multifunction head units — the combined level, temperature, and quality sensor assembly mounted in the DEF tank
• Diesel exhaust fluid sensor heads — standalone level and quality sensors
• DEF header assemblies — tank header/cap assemblies that house the sensor and pickup tube
• DEF doser injectors — the metering injector that delivers fluid into the exhaust stream (Cummins B6.7, L9, X12, X15 and more)
• DEF wiring & tank jumper harnesses — the connecting harnesses between the sensor and the vehicle's ECM

Brands we stock

We carry genuine DEF parts for the OEMs running across North American fleets, including Freightliner, Spartan, Caterpillar, Cummins, International/Navistar, Volvo, Mack, Ford, Hyundai, Doosan, Bobcat, Terex, E-One, Gillig, TEMSA, Stewart & Stevenson, Hollingshead Mixer, Capacity, JLG, Ferrara Fire Apparatus, and Kalmar Ottawa. If you don’t see your exact OEM number listed, search by part number above or contact us — new listings are added regularly.

Why order DEF parts here

• Genuine OEM only — every part is matched to the manufacturer's original part number, not a generic equivalent
• Built for cross-reference — listings include the exact OEM number so you can verify fitment against your service manual or VIN before you buy
• Fleet-ready inventory — broad coverage across trucks, buses, fire apparatus, and off-road equipment, not just one brand
• Fast turnaround — ships quickly to keep your truck off the lift and back on the road

FAQ

What does a DEF multifunction head unit do? It's the sensor assembly mounted in the DEF tank that reports fluid level, temperature, and quality to the ECM. When it fails, the system often can't verify DEF quality and triggers a derate to protect emissions compliance.

How do I know if my DEF sensor is failing? An inaccurate level gauge, a DEF quality fault code, an unexpected derate, or a warning light that won't clear even after refilling with quality fluid.

Genuine OEM or aftermarket? All parts here are genuine OEM — no generic substitutes.

How do I find the right part? Match the OEM number on your old component, or check your service manual/VIN, then search that number above.