US Safety Agency Upgrades Brake Investigation into Over 1 Million GM and Honda Vehicles

The premier auto safety regulator in the United States has escalated its defect probe into braking systems used across a wide range of General Motors electric and internal combustion vehicles, as well as models co-developed with Honda. The upgraded review follows hundreds of logged incidents, more than 20 crashes or fires, and at least six reported injuries.

What Happened

The National Highway Traffic Safety Administration (NHTSA) announced that its Office of Defects Investigation (ODI) has elevated its preliminary evaluation to an “engineering analysis.” This classification represents the agency’s highest investigative tier, an action that frequently precedes a formal manufacturer recall. The agency’s inquiry encompasses potentially more than 1 million vehicles.

NHTSA originally launched its defect inquiry in April 2024 following complaints from owners of the 2023 Cadillac Lyriq. Initial reports to the agency noted dashboard warnings reading “Brake System Failure” upon vehicle startup or after stopping entirely. Internal investigations by GM concluded that issues originated from spindle fractures within the electronic “eBoost” brake-by-wire system. However, ODI subsequently recorded incidents indicating an immediate loss of power brake assist while drivers were actively slowing down—symptoms inconsistent with the spindle failure explanation provided by the automaker.

Key Highlights

• Scope of Inquiry: Over 1 million vehicles are potentially impacted, covering both electric and conventional gasoline models.
• Reported Incidents: Regulators have documented hundreds of complaint incidents, over 20 crashes or fires, and a minimum of six injuries linked to the issue.
• Affected Models: Impacted electric models include the Cadillac Lyriq, Chevrolet Blazer EV, Chevrolet Equinox EV, and Honda partnership vehicles including the Honda Prologue and Acura ZDX. The discontinued autonomous Cruise Origin also utilized the technology.
• Non-EV Vehicles Involved: The investigation extends to traditional combustion models, specifically the Chevrolet Colorado, GMC Canyon, Buick Enclave, and Buick Envision.
• Technological Shift: GM introduced its eBoost brake-by-wire setup in 2019 to replace physical mechanical connections between pedals and brakes with electronic controls, enabling adjustable pedal feel across driving modes.

Why This Matters

The transition toward brake-by-wire setups replaces traditional hydraulic and mechanical pedal linkages with electronic signals. When these systems experience an abrupt loss of brake assistance during deceleration, stopping distances can lengthen substantially. Driver reports submitted to regulators describe severe outcomes, including a 2025 Lyriq crashing through a storefront when brakes failed in a parking lot, and a 2024 Blazer EV owner intentionally steering into a concrete curb to halt the vehicle before entering an intersection.

What to Watch Next

The engineering analysis conducted by NHTSA’s Office of Defects Investigation will evaluate the potential failure modes within GM’s eBoost assembly. If the defect investigation determines that the brake-by-wire hardware or software presents an unreasonable safety hazard, the agency may request or mandate a formal safety recall. General Motors stated that its internal reviews found the condition does not present an unreasonable risk to vehicle safety, while confirming it will continue cooperating with NHTSA throughout the proceeding.

Frequently Asked Questions

What is the eBoost system?

Introduced by GM in 2019, eBoost is a brake-by-wire mechanism that eliminates the direct mechanical linkage between the brake pedal and the braking system, replacing it with an electronic connection that allows customized pedal feel across driving modes.

Which brands and vehicles are affected?

The investigation covers several GM electric vehicles such as the Cadillac Lyriq, Chevy Blazer EV, and Chevy Equinox EV, along with the Honda Prologue and Acura ZDX built under a joint partnership. Non-electric models including the GMC Canyon, Chevy Colorado, Buick Enclave, and Buick Envision are also involved.

What position has General Motors taken regarding the probe?

General Motors stated that customer safety is its top priority, noting that its internal investigations concluded the condition does not pose an unreasonable safety risk. The automaker stated it will continue full cooperation with NHTSA.

Source: TechCrunch reporting on National Highway Traffic Safety Administration documentation and manufacturer statements.