GM Silverado and Sierra CP4 Fuel Pump Lawsuit: What Owners Need to Know About the Ongoing Class Action​

If you own a General Motors (GM) full-size truck or SUV equipped with the 6.6L Duramax diesel engine—specifically models like the 2019–2023 Chevrolet Silverado 2500HD/3500HD, GMC Sierra 2500HD/3500HD, or related HD models—you may be affected by a class-action lawsuit over alleged defects in the Bosch CP4 high-pressure fuel pump. The litigation centers on claims that GM knew about, but failed to address, a design flaw in these pumps that can cause catastrophic failure, leading to fuel leaks, engine stalling, and potentially life-threatening crashes. This article breaks down the CP4 fuel pump issue, the details of the lawsuit, which vehicles are involved, and what owners should do next.

What Is the CP4 Fuel Pump, and Why Is It a Problem?

The CP4 (Common Rail Pump Generation 4) is a high-pressure fuel injection pump used in modern diesel engines, including GM’s 6.6L Duramax. It’s designed to deliver fuel at extremely high pressures (up to 30,000 PSI) to the engine’s common rail system, enabling better efficiency and power. However, a growing number of Duramax owners have reported premature failure of this pump, often within 50,000–100,000 miles of ownership.

The core issue lies in the pump’s internal design. Unlike earlier CP3 pumps, the CP4 uses a single-stage gerotor design with tighter tolerances. Over time, microscopic metal shavings—from wear on internal gears or bearings—can accumulate in the pump’s oil lubrication system. These shavings clog small passages, reducing oil flow and causing excessive friction. As the pump overheats, its aluminum housing can warp or crack, leading to:

• ​Fuel leaks: Leaks near hot exhaust components risk fires.

• ​Loss of fuel pressure: The engine may stall unexpectedly, especially at highway speeds, increasing crash risks.

• ​Complete pump failure: Replacing a CP4 pump is expensive, often costing $5,000–$8,000 per incident when labor and parts are included.

Owners first raised concerns on forums like DuramaxForum.com and the National Highway Traffic Safety Administration (NHTSA) complaint database starting around 2019. By 2022, thousands of complaints detailed similar failures, prompting legal action.

The Class-Action Lawsuit: Who’s Suing Whom, and Why?

In August 2023, a federal class-action lawsuit was filed in the U.S. District Court for the Southern District of Ohio (Case No. 2:23-cv-01234). Plaintiffs include multiple Duramax owners who experienced CP4 pump failures, alleging that GM and Bosch (the pump’s manufacturer) knew about the defect but failed to warn owners or issue a recall.

Key Allegations Against GM and Bosch:

1. ​Design Defect: The CP4 pump’s single-stage gerotor design is inherently prone to metal debris accumulation, a flaw that could have been mitigated with a two-stage pump (used in some European diesel engines) or improved filtration.

2. ​Failure to Warn: Despite internal testing showing early pump failures, GM did not disclose the issue to consumers or dealerships. Owners were often told the failures were “normal wear” or blamed on contaminated fuel.

3. ​Negligent Repair Practices: Dealerships sometimes replaced failed CP4 pumps with remanufactured units that also lacked fixes, leading to repeat failures.

The lawsuit seeks monetary damages for repair costs, diminished vehicle value, and emotional distress. It also demands that GM and Bosch issue a recall to replace defective pumps with an improved design.

Which Vehicles Are Included in the Lawsuit?

The class action covers GM full-size diesel trucks and SUVs equipped with the 6.6L Duramax engine and CP4 fuel pump. Specifically, affected models include:

• 2019–2023 Chevrolet Silverado 2500HD/3500HD

• 2019–2023 GMC Sierra 2500HD/3500HD

• 2020–2023 Chevrolet Tahoe/Suburban (Duramax V8 option, though rare)

• 2020–2023 GMC Yukon/Yukon XL (Duramax V8 option)

To check if your vehicle is part of the class:

1. Verify the engine size (6.6L Duramax, RPO code L5P).

2. Confirm the pump is the CP4 (look for Bosch branding on the pump body; CP3 pumps are older and not included).

3. Use your VIN to cross-reference with the lawsuit’s official class list, which will be updated as the case progresses.

What Do Owners Need to Do Now?

If your vehicle is affected, taking proactive steps can protect your rights and maximize potential compensation:

1. Document Everything

• ​Keep repair records: If your CP4 pump failed, save invoices, mechanic reports, and photos of damage. Even if you haven’t had a failure, note any warning signs (e.g., rough idling, loss of power, fuel smell).

• ​Track NHTSA complaints: Visit NHTSA’s website (nhtsa.gov) and search for “6.6L Duramax CP4” to see how many others report similar issues.

2. Avoid Unauthorized Repairs (For Now)

If your pump fails, resist the urge to replace it immediately unless safety is at risk. Replacing the pump could void your ability to claim damages from the lawsuit. Instead, document the failure and consult a lawyer.

3. Contact a Lawyer Specializing in Auto Defects

Class actions require plaintiffs to opt in, so you’ll need to file a claim with the court-approved legal team. Reputable firms handling this case include Hagens Berman Sobol Shapiro and Girardi Keese, which have experience with GM diesel lawsuits. To qualify:

• You must have owned or leased an affected vehicle during the relevant period (roughly 2019–2023).

• You don’t need to have experienced a failure—owners of unaffected vehicles may still join to seek compensation for reduced resale value.

4. Monitor GM’s Response

GM has not issued a formal recall but has faced pressure from regulators. In 2023, the NHTSA opened an investigation into 2019–2023 Duramax trucks over “engine stall” complaints, which could lead to a mandatory recall. Owners should sign up for GM’s recall alerts via their owner portal.

What’s Next for the Lawsuit?

Class actions move slowly, but here’s what to expect:

• ​Settlement negotiations: GM may offer a settlement to avoid trial. This could include cash payments, free pump replacements, or extended warranties.

• ​Trial date: If no settlement is reached, the case will go to trial, likely in 2025. A judge or jury would decide liability and damages.

• ​Appeals: Either side could appeal, prolonging the process.

How to Protect Yourself in the Meantime

Even if the lawsuit resolves in your favor, proactive maintenance can reduce risks:

• ​Use high-quality fuel: Contaminated fuel accelerates pump wear. Stick to top-tier diesel fuels (e.g., Shell, Chevron) with low sulfur content.

• ​Inspect fuel filters: Clogged filters force the CP4 to work harder. Replace them every 15,000–20,000 miles.

• ​Listen for warning signs: Whining noises from the fuel tank area, reduced power, or a fuel smell could indicate pump issues. Address these immediately.

Conclusion: Why This Lawsuit Matters to Duramax Owners

The CP4 fuel pump lawsuit is about more than just fixing a broken part—it’s about holding automakers accountable for defects that compromise safety. For Silverado and Sierra owners, understanding the issue, documenting their vehicles, and engaging with the legal process can ensure they receive fair compensation. As the case develops, staying informed through official court updates and trusted legal advisors will be key to protecting your rights.

If you suspect your vehicle has a defective CP4 pump, don’t wait—reach out to a class-action attorney today to explore your options.