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Cummins 5509448 is the 12 volt DEF (AdBlue) doser fluid supply module: the black pump and motor housing, the silver centre block with the DEF inlet, outlet and return connectors, and the sealed electrical plug. It is used on Cummins B6.7 and L9 engines. This aftermarket version is made to the same mounting and connections as the original, so it fits where the old one came off.
The same part is also sold as Cummins A063W687.
Sold as one unit. Check the number on your old part, or in the parts manual for your machine, before ordering.
| Part Type | DEF Doser Fluid Supply Module |
| Replaces | Cummins 5509448 |
| Voltage | 12 V |
| Engine | Cummins B6.7 CM2350 B121B, B6.7 CM2450 B155B, L9 CM2450 L126B |
| Cross references | Cummins A063W687 |
| Fits | Cummins B6.7 CM2350 B121B, B6.7 CM2450 B155B and L9 CM2450 L126B engines, including Peterbilt 567 and 579 trucks |
| Condition | New, aftermarket |
| Stat. HS-Code | 841330 |
| Country of Manufacture | China |
Cummins machines
Check the part number on your old unit before ordering.
| Cummins Part No.(SPM Part No.) | Fits |
|---|---|
| 5509448(SPM-HEP-5238) | Cummins B6.7 CM2350 B121B, B6.7 CM2450 B155B and L9 CM2450 L126B engines, including Peterbilt 567 and 579 trucks |
| A063W687(SPM-HEP-5238) | Cummins B6.7 CM2350 B121B, B6.7 CM2450 B155B and L9 CM2450 L126B engines, including Peterbilt 567 and 579 trucks |
Low DEF pressure fault
A worn pump motor or diaphragm cannot build dosing pressure, and the engine logs an SCR or DEF pressure fault.
Engine derate
When DEF is not dosed the aftertreatment system cuts engine power until the fault is fixed.
Crystallised or frozen DEF
Dried urea crystals and freezing damage the pump and its check valves. Replace the pump if flushing does not clear the fault.
Fitting tips
Disconnect the battery, clean the DEF line connectors before opening them, fit the new pump with new seals and run the DEF priming test.
We check what other aftermarket sellers charge for this same part. Their prices on the date we checked:
| Seller | Price | Checked |
|---|---|---|
| SINOCMP | USD 369.00 | 3 Nov 2026 |
| Amazon (NETYANPI) | USD 370.25 | 3 Nov 2026 |
| Amazon (FLIBEN) | USD 433.46 | 3 Nov 2026 |
| eBay, aftermarket seller | USD 440.95 | 3 Nov 2026 |
| Amazon (YIHETOP) | USD 446.51 | 3 Nov 2026 |
| FridayParts | USD 729.75 | 3 Nov 2026 |
| Spare Part Mart | USD 295.20 | Today |
Our price of USD 295.20 is 20% to 60% less than these sellers.
Found this part cheaper somewhere else? Send us the listing and we will beat it by 5% under our Price Beat Guarantee. Every order is also covered by our 30 day money back guarantee.
Yes, it was made for the Cummins B6.7 CM2350 B121B, and 4 more listed under compatible equipment. Check the old def pump is marked 5509448 or one of the cross references, because makers change parts between serial ranges.
On the Cummins B6.7 CM2350 B121B, often 5,000 to 10,000 hours with clean fluid, much less with dirt or air in the system. It is usually changed on condition, not by hours.
Leaks from the seal or weep hole, noise or whining, overheating, or falling pressure or flow under load.
Yes. Fill the pump and its suction line with clean fluid before the first start. Running it dry, even for a few seconds, can score it.
Clean them right back to metal and fit the new gasket or O-ring dry, unless the engine manual calls for sealant.
No. It is an aftermarket def pump made to replace the Cummins 5509448. It is not made by the original manufacturer; the number only shows what it replaces.
Live rates for the quantity selected, delivered to your door. Confirmed at checkout.
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