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The ongoing saga of the Bosch CP4 fuel pump in Chevrolet Silverado Duramax diesel engines has ramped up. After a March 2023 lawsuit over the same fuel pump in Nissan Titan pickups comes lawsuit state certification for General Motors Duramax engines with the CP4 pump. The Duramax class-action lawsuit is now certified in seven states. 

What year Silverado and Sierra Duramax trucks are affected?

2016 Chevrolet Silverado 2500 HD Duramax diesel
2016 Chevrolet Silverado 3500 HD | General Motors

This lawsuit centers around 2011 to 2016 Chevrolet Silverado and GMC Sierra pickups with a 6.6-liter LML V8 Duramax turbodiesel engine. The CP4 fuel pump replaced the CP3 pump in 2011. Claims of defects did not affect the previous CP3 units.

The class-action lawsuit argues that the CP4 pump is prone to premature wear caused by diesel fuel sold in the United States. Allegedly, U.S. diesel fuel is drier than in other parts of the world. The result is that non-U.S. diesel fuel lubrication qualities help maintain longevity.

In which states is the Duramax lawsuit certified?

2016 GMC Sierra HD All-Terrain Duramax
2016 GMC Sierra HD All-Terrain Duramax | General Motors

When U.S. diesel fuel begins to degrade the materials in the CP4 pumps, it causes metal shavings to travel through the fuel system. That can lead to damage to the fuel system and the Duramax engine. Drivers experience loss of power or engine stalls. The lawsuit also claims GM has known about the issue but chose not to do anything about it. Allegedly, the automaker hid the problem from buyers. 

The states in which the class-action lawsuit has been certified are California, Florida, Illinois, Iowa, New York, Pennsylvania, and Texas. It was originally filed in the U.S. District Court for the Eastern District of Michigan. 

The Bosche CP4 fuel pump has a storied past. On Mar. 23, 2023, a similar class-action lawsuit was filed against Nissan and Cummins Inc. Cummins supplied its 5.0-liter turbodiesel V8 to Nissan for Titan HD pickup trucks built between 2016 and 2019. After 2019, Nissan offered only its 5.6-liter gas engine in the Titan.

Is the same Bosch fuel pump used in other makes?

In June and October 2022, Ram issued recalls for its Cummins diesel engines equipped with the same CP4 Bosch fuel pump. The recall included over 222,000 Ram 2500 and 3500 pickups and 3500, 4500, and 5500 chassis cabs with the 6.7-liter turbodiesel engine. Dealers replaced the fuel pump under warranty. If other components were damaged, they were also replaced for free. Ram said it became aware of the problem in October 2021. 

In March 2023, the National Highway Traffic Safety Administration expanded its investigation into the CP4 fuel pump issues. Besides the aforementioned vehicles potentially affected, the NHTSA probe also includes several BMW diesel models built between 2014 and 2018. BMW issued a recall in August 2021 for those models. 

So GM’s and Nissan’s handling of the CP4 problem is completely different from BMW’s and Ram’s approaches. 

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Thom Taylor

Thom Taylor is a celebrated automotive journalist. He was awarded the Top 100 Most Influential People in Hot Rodding from Hot Rod Magazine, and was inducted into the Grand National Roadster Show Hall of Fame and the National Rod and Custom Hall of Fame. He’s a member of SEMA and the NHRA.

Thom has authored a number of books, including Hot Rod & Custom Chronicle and several guides for drawing vehicles like a pro, which pull from his distinguished ventures as an automotive illustrator.

Thom joined the MotorBiscuit team in 2019, and focuses his coverage on new vehicle releases, design, and the latest features and tech in the industry. His tenure of 25 years writing about the industry gives him a unique context for the auto news he covers, whether it’s part of the Rusty Monday series or the latest news from Chevy. Thom has built two complete cars from the ground up and driven vintage roadsters at the Indy 500.