Restore high-pressure fuel delivery, stable rail pressure, and dependable performance on your 2011-2016 GM 6.6L Duramax LML/LGH with this genuine Bosch OE remanufactured CP4 fuel injection pump. This direct-replacement pump helps correct fuel system concerns such as hard starting, low rail pressure, poor throttle response, reduced power, fuel pressure codes, and drivability issues under load. Bosch: 0986437421, 0 986 437 421 Installation Note: Verify fuel system contamination, filtration, and related rail pressure diagnostics before installation. Fitment Note: Verify build date, VIN, engine application, emissions package, and existing pump part number before ordering. Core Charge Notice: Core return required. A refundable core deposit will be applied at checkout and refunded after receipt and approval of a rebuildable core.