Federal safety officials suspect corrosion makes the anti-lock brakes prone to fail in some 3.6 million sport utility vehicles and pickup trucks built by General Motors in the early 1990s.
Agency officials have told GM of their findings, although they are not to the point of ordering any action.GM officials say that even if some brake valves were corroded, "these vehicles still have good braking capability."
The agency has discussed where the investigation stands with the company but has stopped short of publicly announcing any findings.
GM spokesman Kyle Johnson said the National Highway Traffic Safety Administration has been investigating corrosion "as a possible performance condition that they think might be a cause of brake complaints."
Patrick Fitzgerald, a spokesman in Livonia, Mich., for LucasVarity, which makes Kelsey-Hayes brand brakes, said the corrosion "hypothesis has been tested and refuted by our company and by General Motors."
The anti-lock brake investigation is the longest still open at the highway safety agency. There have been 15,400 complaints about the Kelsey-Hayes brakes, the largest number of complaints for any current agency investigation.
Consumers have reported 2,728 crashes they claim were caused by faulty anti-lock brakes and 437 injuries, according to NHTSA.
The vehicles under investigation are the 1991-94 Chevrolet Blazer, GMC Jimmy, Oldsmobile Bravada and Typhoon sport utility vehicles; the Chevrolet S-10, Sonoma and Cyclone pickup trucks; and 1992-94 Chevrolet and GMC Suburban sport utility vehicles.