When your International or Navistar chassis is paired with a Cummins engine, one of the most critical—but often overlooked—components within your emissions setup is the DEF (Diesel Exhaust Fluid) head unit. The Navistar/International Cummins DEF Head Unit, built to OEM 2515900C1 (Tamerx part 5410-11-FA01-4), is the module that monitors fluid properties and enables accurate dosing. When it fails or drifts out of spec, your engine control system loses confidence in your DEF readings—and that’s when fault codes, derates, or emissions warnings start to surface.
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Reads DEF fluid level, temperature, and urea concentration, providing accurate feedback to the engine’s ECU
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Governs precise dosing of DEF into the exhaust stream so the SCR (Selective Catalytic Reduction) system can reduce NOx properly
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Manufactured to OEM 2515900C1 tolerance for plug-and-play compatibility in Navistar / International Cummins setups
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Helps prevent emission system warnings, fault codes, or engine derates that stem from bad sensor feedback
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Built to withstand real-world conditions: vibration, thermal cycling, and exposure to corrosive DEF chemistry
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Field-friendly design reduces installation time and supports more reliable diagnostics
A failing DEF head often doesn’t show dramatic symptoms until it triggers a check engine light or the system goes into limp mode. By installing the correct OEM 2515900C1 / Tamerx 5410-11-FA01-4 unit, you restore precision to your emissions feedback loop, protect your SCR system, and reduce the risk of surprise maintenance events. In the world of modern emissions systems, this modest device is one you can’t afford to neglect.