Description: Fluid Supply Doser Module
Condition: New
Brand: Cummins
Part Number: 5373865
Vehicle Fitment 5373865:
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Medium-Duty (6.7L Engines):
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Platforms: Cummins ISB6.7, QSB6.7.
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Common Part Numbers: 4387304, 5273338, 4375026.
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Vehicles: School buses (Blue Bird, Thomas), Freightliner M2 106, Ford F-650/750, and medium-duty Ram trucks (Chassis Cab).
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Heavy-Duty (12L & 15L Engines):
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Platforms: Cummins ISX15, X15, QSX15, ISX12.
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Common Part Numbers: 5511749, 4394627, 4387658.
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Vehicles: Class 8 trucks like Kenworth T680, Peterbilt 579, Freightliner Cascadia, and International LT Series.
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Industrial/Tier 4 Platforms:
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Platforms: Cummins B4.5, F3.8, L9.
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Common Part Numbers: 5418806, 5375352 (This part number is very close to the one you mentioned earlier).
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The Fluid Supply Doser Module 5373865 often referred to as the DEF Pump or Urea Pump, is the "heart" of the Selective Catalytic Reduction (SCR) system. Its primary role is to manage the delivery of Diesel Exhaust Fluid (DEF) to the exhaust stream to reduce harmful nitrogen oxide (NOx) emissions.
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Pressurization: The module draws DEF from the storage tank and pressurizes it (usually to around 9 bar / 130 psi) so it can be finely misted by the injector.
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Purge Cycle: One of its most important features is the "purge" function. When the engine is turned off, the module pumps the remaining fluid back into the tank. This prevents the DEF from freezing or crystallizing inside the lines, which could crack the module.
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Filtering: It contains an internal main filter to protect the precise dosing mechanism from contaminants or crystallized urea.
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Electronic Control: It communicates directly with the Engine Control Module (ECM) via the CAN bus to determine exactly how much fluid is needed based on engine load and NOx sensor readings.
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Signs of Faulty 5373865:
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DEF Pressure Faults: If the module cannot reach or maintain its operating pressure (typically around 130 psi / 9 bar), the ECM will trigger fault codes like 3558 or 3559. You may hear the pump "hunting" or running constantly without building pressure.
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Crystallization Leaks: White, chalky deposits around the module's fittings or the vent hole indicate that DEF is leaking. Once the fluid dries and crystallizes, it can seize the internal pump mechanism or damage the electrical circuit board.
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Failed Purge Cycle: If you don't hear the characteristic "clicking" or humming sound of the pump running for 30–60 seconds after you turn off the ignition, the purge cycle has failed. This usually leads to frozen or clogged lines in cold weather.
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Low DEF Consumption: If you notice that you are rarely needing to refill your DEF tank, the module is likely not delivering fluid. This will eventually lead to a NOx conversion error and a 5-mph derate.
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Electrical Communication Codes: Fault codes like 3591 indicate the module has lost communication with the engine via the CAN bus, often due to internal short-circuiting from moisture or vibration.
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Manufacturer information
Cummins® is a worldwide leader in the production of engines, agricultural components, and other power-generating devices for various industries, including medium and heavy duty trucks, light commercial vehicles, buses, agriculture, and construction. Founded in 1919, this company stays true to its mission of making people's lives better by continuously improving its product line-up and introducing new solutions for a more prosperous world. Its core values—integrity, diversity and inclusion, excellence, caring, and teamwork—are what make it a successful company today—a worldwide leader with a network of more than 600 company-owned and independent distributors and almost 6,000 dealers in approximately 190 countries.
Warranty
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