The ongoing saga of the Bosch CP4 fuel pump used 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 GM Duramax engines with the CP4 pump. The Duramax class action lawsuit is now certified in seven states. 

What year Silverado and Sierra trucks are affected?

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

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

Which states are the lawsuit certified in?

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

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

The Bosche CP4 fuel pump has quite a storied past. On March 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 its Titan HD pickup trucks built between 2016 and 2019. After 2019, Nissan only offered its 5.6-liter gas engine in the Titan.

Is the same Bosch fuel pump used in other makes?

In June and then again in October of 2022, Ram issued recalls for its Cummins diesel engines equipped with the same CP4 Bosch fuel pump. Over 222,000 Ram 2500 and 3500 pickups and 3500, 4500, and 5500 chassis cabs with the 6.7-liter turbodiesel engine. Ram dealers replaced the fuel pump under warranty. If other components were damaged these were also replaced for free. Ram first became aware of the problem in October 2021. 

Last month 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 through 2018. BMW issued a recall in August 2021 for those models affected. 

So the handling of the CP4 problem by GM and Nissan is completely different than BMW and Ram’s approach.