CP4 Fuel Pump Silverado Sierra Lawsuit USA
What is the CP4?
The Bosch CP4 (also called CP4.1 or CP4.2) is a high-pressure common-rail fuel injection pump. GM introduced it in the 2011 Duramax LML 6.6L diesel engine, replacing the more robust Bosch CP3 pump that had powered previous Duramax engines (LB7, LLY, LBZ, LMM).
Why Does It Fail in U.S. Trucks?
The CP4 was originally engineered for European diesel fuel, which has a higher lubricity (slipperiness) than U.S. Ultra-Low Sulfur Diesel (ULSD). The CP4 relies on the fuel itself for internal lubrication of its precision metal components. U.S. ULSD, while cleaner for emissions, lacks sufficient lubricity to adequately lubricate the pump’s internal cam and roller assembly.
Over time — sometimes within 100,000 miles, sometimes much sooner — the metal components wear and fracture. Metal shards (debris) are then pumped at high pressure throughout the entire fuel system: injectors, fuel rails, lines, and the fuel tank. The contamination is catastrophic and typically requires replacement of the entire high-pressure fuel system.
CP4.1 vs CP4.2
- CP4.1: Single piston; slightly less output; used in some light-duty applications
- CP4.2: Dual piston; higher output; used in GM Duramax LML and L5P engines; more common in the lawsuit context
- Both share the same fundamental design flaw regarding lubricity requirements
Why Not Just Replace the Pump?
Because metal debris circulates through the entire fuel system, replacing only the pump is insufficient. Repair typically requires replacing:
- High-pressure fuel pump
- Fuel injectors (all)
- High-pressure fuel rails
- Fuel lines
- Fuel tank (in severe cases) Total repair cost: 20,000+ depending on extent of damage and labor rates
Affected Vehicles (Model Years & Engines)
| Vehicle | Engine | Model Years |
| Chevrolet Silverado 2500HD | 6.6L Duramax LML | 2011–2016 |
| Chevrolet Silverado 3500HD | 6.6L Duramax LML | 2011–2016 |
| GMC Sierra 2500HD | 6.6L Duramax LML | 2011–2016 |
| GMC Sierra 3500HD | 6.6L Duramax LML | 2011–2016 |
Note: The 2017–present L5P Duramax also uses a variant of the CP4.2, though the primary lawsuit focus is 2011–2016 LML engines. Some sources include 2017–2019 as secondary affected years.
Also affected (outside the GM lawsuit):
- Ford F-250/350 Power Stroke 6.7L diesel (2011–2019) — separate Ford lawsuit
- Ram 2500/3500 Cummins diesel — separate proceedings
Lawsuit Legal Details
Case Name: Counts v. General Motors, LLC (primary case); also In re: General Motors LLC CP4 Fuel Pump Litigation
Filed: 2018 in U.S. District Court, Eastern District of Michigan
Lead Plaintiffs’ Firm: Hagens Berman Sobol Shapiro LLP (prominent class action firm)
What Was Alleged:
- GM knowingly sold vehicles with a defective fuel pump
- GM was aware CP4 was incompatible with U.S. ULSD fuel
- GM concealed this defect from consumers
- Violation of implied warranty of merchantability
- Violations of state consumer protection statutes
- Fraudulent concealment / unjust enrichment
2021 — Partial Dismissal: The Eastern District of Michigan dismissed some claims in 2021 but allowed others to proceed, particularly breach of warranty claims.
Appeal: Plaintiffs appealed the dismissed portions to the Sixth Circuit Court of Appeals.
Settlement (2022–2023): A class action settlement was reached. Key terms:
- Settlement Fund: Approximately 40 million total (exact figures varied by reporting)
- Eligible Claimants: Owners/lessees of affected 2011–2016 Duramax Silverado/Sierra who experienced CP4 failure and paid for repairs
- Reimbursement: Up to a percentage of documented repair costs (not 100% — typical class action recovery)
- Extended Warranty Component: Some coverage extended for qualifying vehicles that hadn’t yet experienced failure
- GM Admission: GM denied all wrongdoing as part of the settlement
Claim Deadline: Most settlement claim deadlines were in 2023–2024 (specific dates varied by settlement administrator notice)
Symptoms of CP4 Pump Failure
- Hard start or no-start — especially when cold
- Loss of power / poor acceleration — fuel pressure drops
- Excessive smoke (black or white) from exhaust
- Rough idle or engine misfires
- Check Engine Light (CEL) — multiple fuel system codes
- Metal shavings in fuel filter — often discovered during routine service
- Sudden catastrophic stall — complete pump failure while driving
- Fuel injector failure — caused by debris contamination
GM Technical Service Bulletins (TSBs)
GM issued TSB #14-06-04-002 acknowledging hard starts related to fuel quality and recommending the use of fuel additives (lubricity improvers). Critics argue this TSB was GM’s acknowledgment of the underlying design defect while not actually solving it.
Repair Costs
| Repair Scenario | Estimated Cost |
| Pump only (if caught early, no contamination) | 4,000 |
| Pump + injectors | 10,000 |
| Full system replacement (pump, injectors, rails, tank) | 20,000+ |
| CP3 conversion kit (preventive) | 4,000 |
CP4 vs CP3 Comparison
| Feature | CP3 | CP4 |
| Design origin | Late 1990s, robust design | European market, lightweight |
| Lubricity requirement | Lower — more tolerant of ULSD | Higher — requires European diesel |
| Failure rate in U.S. | Very low | Significantly higher |
| Output | Lower pressure | Higher pressure (more efficient) |
| Cost to replace | ~2,500 | 4,000+ |
| Self-lubricating? | More tolerant | Relies heavily on fuel lubricity |
Prevention Tips
- Use lubricity additives (e.g., Stanadyne, Opti-Lube).
- Install CP3 conversion kits proactively.
- Filter fuel religiously; test for shavings early.
Conclusion – CP4 Fuel Pump Silverado Sierra Lawsuit
The CP4’s mismatch with U.S. ULSD turned a promising pump into a diesel owner’s nightmare, sparking lawsuits and $20K repair bills—but conversions to CP3 and additives offer reliable fixes. If your 2011–2016 Duramax shows symptoms, inspect immediately to avoid catastrophe. Upgrading now saves thousands long-term.