GM 1.2L I3 Engine Failure Lawsuit: Vehicles and Warranty Denials

A class action filed in March 2026, Cook v. General Motors LLC, accuses GM of knowingly selling small SUVs with a defective 1.2-liter turbocharged three-cylinder engine that can fail catastrophically at low mileage. The GM 1.2L I3 engine failure lawsuit covers 2024-and-newer Chevrolet Trax, Chevrolet Trailblazer, Buick Encore, and Buick Envista models, and alleges connecting-rod failures, oil leaks, sudden power loss, and in some cases fires.¹

Which Vehicles Are Covered

The proposed class is limited to 2024 and newer model-year examples of four vehicles: the Chevrolet Trax, Chevrolet Trailblazer, Buick Encore, and Buick Envista. All share GM’s 1.2-liter turbocharged inline-three, built under RPO codes LIH and LBP, rated at 137 horsepower and 162 pound-feet of torque.²¹

What the Lawsuit Says Is Wrong With the Engine

The 56-page complaint points to defective bearings, improperly designed lubrication passages, and flawed casting features that the plaintiffs say cause oil starvation, bearing damage, and connecting-rod failure. Engine-block porosity is cited as another contributing factor.³

Owners describe a consistent pattern. A loud knocking or banging noise. A “reduced engine power” warning on the dash. Then total loss of power. In the most severe failures, the complaint says a broken connecting rod punches through the engine block, and the resulting fluid leaks can cause smoke or fire. The complete loss of engine power also kills power steering assist, which the plaintiffs say makes the vehicle hard to control as it coasts to a stop.¹

Lead plaintiff Samantha Cook reported that her 2024 Chevrolet Trax threw a reduced-power warning and began knocking loudly on January 25, 2026, at 11,581 miles. The dealer found a broken connecting rod and block damage requiring a full engine replacement.⁴

What GM Allegedly Knew

The plaintiffs claim GM has known about the defect “since at least 2022, if not earlier,” based on pre-release testing, warranty claims, and dealer repair reports.¹

The complaint identifies four Technical Service Bulletins GM issued to dealers about the engine: 20-NA-084, 23-NA-122, 23-NA-141, and 24-NA-021.³ Bulletin 20-NA-084, revised in April 2025, tells dealers that a “deep thudding” noise under low-speed acceleration is “inherent to this small-displacement, power-dense engine design” and that “no parts are required for this repair.”⁵ Bulletin 23-NA-122 addresses oil leaks caused by porosity in engine-block bolt holes and directs technicians to seal the affected bolt with Loctite rather than replace the engine.⁶

According to the lawsuit, GM instructed dealers to tell customers reporting these symptoms that their vehicles were “operating normally” or “operating as intended,” which the plaintiffs say was used to deny warranty coverage for a known defect.⁴

Warranty Denials and Replacement Engine Backorders

The affected vehicles are inside GM’s five-year, 60,000-mile powertrain warranty, but the lawsuit says some owners have paid out of pocket because warranty claims were denied or repairs were limited to fixes that did not address the underlying problem.⁴

Owners whose claims are approved face a different problem: replacement engines are on extended backorder with no confirmed arrival dates. The complaint calls the wait “multiple months long.” One owner reported their vehicle sitting at a dealership for 39 days awaiting a new engine; Samantha Cook’s Trax was left stranded at the dealer with no delivery date for the replacement.⁷⁴ NHTSA complaint data for the 2024 Trax shows similar reports of catastrophic failure, stalling in traffic, and extended repair waits, with one consumer noting that GM “is aware of the problem but has not issued a recall.”⁸

What the Lawsuit Is Asking For

The complaint brings claims under the federal Magnuson-Moss Warranty Act and California consumer protection laws, including the Song-Beverly Consumer Warranty Act, the California Business and Professions Code, and the Consumers Legal Remedies Act. It also alleges breach of warranty, fraud, and unjust enrichment.⁹

The plaintiffs seek declaratory and injunctive relief along with compensatory, exemplary, and statutory damages for the class. They argue owners would not have bought the vehicles, or would have paid less, had the defect been disclosed, and that they are entitled to reimbursement for engine replacement costs and related damage.¹⁰

Where the Case Stands

The case was filed on March 4, 2026, in the U.S. District Court for the District of Delaware and amended on May 1, 2026, to add additional plaintiffs. GM entered an appearance in April 2026 through outside counsel, and the court has approved a joint stipulation on initial deadlines. The case has not reached discovery, and no motion to dismiss, scheduling order for trial, or settlement talks have been reported.¹¹ GM has not publicly commented on the allegations, and multiple outlets have reported the company did not respond to requests for comment.⁷

1
ClassAction.org. GM Lawsuit Alleges Certain Buick, Chevy Vehicles Prone to Catastrophic Engine Failure
2
GM Authority. GM 1.2L Turbo I3 LIH Engine
3
CarComplaints.com. GM 1.2-Liter Turbo Engine Problems Class Action Lawsuit
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GM Authority. GM Hit With Turbo 1.2L I3 Engine Failure Lawsuit
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NHTSA. TSB 20-NA-084
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NHTSA. TSB 23-NA-122
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CarBuzz. General Motors Turbo Three-Cylinder Engine Lawsuit
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CarComplaints.com. 2024 Chevrolet Trax Engine Problems
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Top Class Actions. GM Class Action Claims Trax, Trailblazer, Other Vehicles Have Defective Engines
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ClassAction.org. Cook v. General Motors LLC Complaint
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PACER Monitor. Cook et al v. General Motors LLC