General Motors is facing intensified scrutiny from federal safety regulators over braking problems in more than 1 million vehicles, including many of its newest electric models and several gasoline-powered trucks and SUVs.

The National Highway Traffic Safety Administration has escalated its probe of GM’s “eBoost” brake-by-wire system to an engineering analysis, the agency’s most serious investigative phase before a potential recall. The move follows hundreds of consumer complaints, more than 20 reported crashes or fires, and at least six injuries.

The investigation began after owners of 2023 Cadillac Lyriq electric SUVs reported alarming “Brake System Failure” warnings at startup or after coming to a stop. GM’s internal reviews initially traced the problem to fractures in a spindle within the eBoost unit, which replaces the traditional mechanical link between the brake pedal and the hydraulic system with an electronic interface.

But regulators say subsequent reports point to a broader safety risk. Drivers have described a sudden and complete loss of brake assist while actively slowing down, forcing them to rely on unassisted braking and dramatically lengthening stopping distances. NHTSA says that scenario significantly raises the risk of crashes and injuries and does not fully align with GM’s explanation of spindle failures.

The eBoost system, introduced in 2019, underpins braking in many of GM’s flagship EVs, including the Chevrolet Blazer EV and Equinox EV, the Cadillac Lyriq, and the Honda Prologue and Acura ZDX, which were developed with Honda. It also appears in some internal-combustion models such as the Chevrolet Colorado, GMC Canyon, and Buick Enclave and Envision.

In one incident reported to regulators, the driver of a 2025 Cadillac Lyriq said the vehicle lost braking power while pulling into a parking space, jumped a curb, and crashed through a storefront, coming to rest inside the building. In another, a 2024 Blazer EV driver said they intentionally steered into a concrete curb to stop the vehicle and avoid what they described as a potentially catastrophic collision at an intersection.

The engineering analysis will examine whether the eBoost system has additional failure modes beyond those identified by GM and whether a recall or other corrective action is warranted. GM has said it is cooperating with the investigation while continuing to monitor field data and customer reports.