CP4 Fuel Pump Silverado Sierra Lawsuit: A Comprehensive Guide for Owners

A significant class-action lawsuit has been successfully resolved, alleging that the CP4 high-pressure fuel pump installed in millions of GM Silverado and Sierra trucks with Duramax diesel engines is fundamentally defective. This defect can lead to sudden, catastrophic failure without warning, resulting in repair costs often exceeding $10,000. General Motors (GM) has agreed to a massive settlement to compensate owners of affected 2011-2016 model year trucks. If you own a Chevrolet Silverado 2500/3500 or GMC Sierra 2500/3500 equipped with a 6.6L Duramax LGH, LML, or L5P engine, your vehicle is likely part of this settlement, and you may be entitled to substantial financial reimbursement for past repairs or future protection.

This article provides a complete, factual breakdown of the CP4 fuel pump lawsuit, the nature of the defect, the specific models involved, the details of the settlement, and the critical steps you should take to protect your vehicle and your finances.

​The Core Problem: Understanding the CP4 Fuel Pump Defect​

The CP4 fuel pump, manufactured by German company Bosch, is a high-pressure fuel injection pump. Its job is to take diesel fuel from the tank and pressurize it to extremely high levels before sending it to the fuel injectors for combustion. In many diesel applications worldwide, the CP4 has a history of performance issues. The primary allegation in the lawsuit against GM was that the CP4 pump's design was ​inherently flawed​ and unsuitable for the North American fuel market.

Unlike some other regions, diesel fuel in the United States and Canada has lower lubricity, meaning it is less "slippery." The design of the CP4 pump relies heavily on the lubricating properties of the fuel to keep its internal components from wearing out. When used with lower-lubricity fuel, critical internal parts, such as the plunger and barrel, can experience ​catastrophic metal-on-metal contact. This friction generates fine metallic debris that is then circulated throughout the entire high-pressure fuel system.

This contamination, often called "fuel system glitter," is the root of the problem. The metallic shavings can clog and destroy fuel injectors, damage the high-pressure fuel rails, and contaminate the fuel lines and tank. A failure does not merely mean replacing a single pump; it typically requires a complete and very expensive fuel system overhaul.

​Symptoms of a Failing CP4 Fuel Pump​

Recognizing the early warning signs of a CP4 pump on the verge of failure can potentially save you from a complete breakdown and more extensive damage. It is crucial to address these symptoms immediately.

• ​Loss of Power:​​ The truck may feel sluggish, struggle to maintain speed on inclines, or fail to accelerate as expected.
• ​Difficulty Starting:​​ The engine may crank for a longer time than usual before starting, or it may not start at all.
• ​Engine Misfires or Rough Idling:​​ The engine may run unevenly, shake, or stumble at idle or under light throttle.
• ​Excessive Noise from the Engine Bay:​​ You might hear a loud whining, grinding, or knocking noise coming from the vicinity of the fuel pump, which is distinct from normal diesel engine sounds.
• ​Check Engine Light:​​ The illumination of the check engine light, often accompanied by diagnostic trouble codes related to low fuel rail pressure.
• ​Stalling:​​ The engine may suddenly stall while driving, which can be a significant safety hazard.

It is important to note that in many cases, the pump fails with ​little to no warning. The first sign a driver experiences is the engine shutting down and refusing to restart.

​Models Affected by the CP4 Fuel Pump Lawsuit​

The class-action lawsuit specifically targeted certain model years of heavy-duty trucks. If you own one of the following vehicles, you are likely a class member:

• ​2011-2016 Chevrolet Silverado 2500 HD and 3500 HD​ with the 6.6L Duramax diesel engine (LGH, LML engines).
• ​2011-2016 GMC Sierra 2500 HD and 3500 HD​ with the 6.6L Duramax diesel engine (LGH, LML engines).

It is critical to understand that while the L5P engine (introduced in 2017) also initially used a version of the CP4 pump, it was not included in this specific lawsuit. However, many owners and technicians report similar concerns, and GM later switched to a different pump design in newer L5P models. If you have a 2017 or newer truck, you should research the specific pump installed in your vehicle.

​The Lawsuit Allegations and GM's Response​

The plaintiffs in the lawsuit made several key allegations against General Motors. They argued that GM knew or should have known about the CP4 pump's design flaws and its incompatibility with American diesel fuel before installing it in their trucks. The lawsuit claimed that GM was aware of the widespread failures but ​concealed this information from consumers, marketing the trucks as reliable and durable.

Furthermore, the plaintiffs alleged that when the pumps failed, GM and its dealerships placed the entire financial burden on consumers for repairs that should have been covered under warranty due to a manufacturing defect. The average cost of a full fuel system replacement after a CP4 failure was frequently quoted between ​​$8,000and$12,000.

GM denied these allegations and did not admit any wrongdoing as part of the settlement agreement. However, the company agreed to create a settlement fund to resolve the litigation and provide benefits to affected customers.

​Details of the CP4 Pump Settlement Agreement​

The settlement, which received final approval from the court, establishes a fund to provide monetary relief to class members. The benefits are divided into two main categories: reimbursement for past repairs and extended warranty coverage for future failures.

​1. Reimbursement for Past Repairs:​​
If you paid out-of-pocket to repair a CP4 fuel pump failure on your eligible truck before the settlement date, you can file a claim for reimbursement. The amount reimbursed depends on the mileage on your vehicle at the time of the repair and the total amount you paid. The settlement provides a detailed reimbursement schedule, but generally, you can recover a significant percentage of your repair costs, even if the repair was performed at an independent shop. You will need to provide proof of ownership, proof of payment, and repair invoices.

​2. Extended Warranty Coverage:​​
This is a crucial part of the settlement. For eligible trucks, GM is providing an ​extended warranty specific to the high-pressure fuel system. This warranty coverage is extended to ​10 years or 200,000 miles from the vehicle's original in-service date, whichever comes first. If your CP4 pump fails within this period, GM will cover the cost of repairs, including parts and labor. This provides significant peace of mind for current owners.

​What Should You Do as a Silverado or Sierra Owner?​​

Your course of action depends on your specific situation.

• ​If You Have Already Experienced a Failure:​​ Gather all your repair records, invoices, and proof of payment. You can file a claim for reimbursement through the official settlement website. Be mindful of the deadline for submitting claims, which is strictly enforced.

• ​If You Currently Own an Affected Truck:​​ First, verify your vehicle's eligibility using your VIN on the settlement administrator's website. Understand that your fuel system is now covered by the extended warranty up to 200,000 miles. However, you should also consider proactive measures to prevent a failure, as a breakdown can still be highly inconvenient and potentially dangerous.

• ​Proactive Prevention Strategies:​​ Many diesel experts and owners recommend taking steps to mitigate the risk of a CP4 failure. The most effective and highly recommended solution is to install a ​CP4 failure prevention kit. These kits typically include a ​lift pump​ and a ​filtration system. A lift pump supplies a consistent flow of fuel to the high-pressure CP4 pump, preventing it from running dry, which can accelerate wear. Advanced filtration can help remove contaminants before they reach the sensitive pump internals. While not a guarantee, these systems significantly reduce the risk of a catastrophic failure.

​The Alternative: The CP3 Conversion​

For owners seeking the ultimate peace of mind, a popular and permanent solution is to replace the defective CP4 pump with a proven and reliable ​CP3 fuel pump. The CP3 pump was used in earlier Duramax engines and has an exceptional reputation for durability and reliability. It is far less susceptible to failures related to fuel lubricity.

A ​CP3 conversion kit​ allows you to swap out the CP4 for a CP3. While this is an upfront investment, often costing between $2,000and$3,500 for parts and labor, it is widely considered a wise investment to protect a $10,000+ fuel system and eliminate the anxiety associated with the CP4 defect. Many owners view this as a cost-effective alternative to a potential future failure, especially for trucks that are used for critical tasks like towing or are driven in remote areas.

​Conclusion: Protecting Your Investment​

The resolution of the CP4 fuel pump lawsuit is a significant victory for owners of GM's heavy-duty trucks. It formally acknowledges a serious problem and provides a framework for financial compensation. If you own an affected 2011-2016 Chevrolet Silverado HD or GMC Sierra HD, you must take action to understand your rights under the settlement.

Check your VIN to confirm your truck's status. If you have paid for repairs, file a claim for reimbursement before the deadline. Most importantly, utilize the extended warranty protection and seriously consider proactive measures like a prevention kit or a CP3 conversion to safeguard your vehicle's reliability and your financial well-being. The CP4 issue is a documented engineering flaw, but with the settlement and available aftermarket solutions, owners are no longer powerless against it.