The National Highway Traffic Safety Administration, which made the announcement Wednesday, launched the probe after receiving reports of performance problems on an array of GM vehicles manufactured in the 1990s.
Currently, the agency has on file 10,861 reports of brake problems on General Motors S and T trucks, which included reports of 2,111 crashes and 293 injuries. The agency has also received but not confirmed 2,400 reports of brake problems in Chevrolet Suburbans equipped with anti-lock brakes. In both cases, Kelsey-Hayes built the units.
The vehicles under investigation include the 1991-97 Chevrolet Blazer, GMC Jimmy and the Oldsmobile Bravada sport utility vehicles; the Chevrolet S-10 and GMC Sonoma, Cyclone and Typhoon pickup trucks; and the 1992-95 Chevrolet and GMC Suburban sport utility vehicles.
In the complaints, some customers said they were attempting to stop at a stop sign or traffic light when the anti-lock brake system failed to respond or locked up, and their vehicle went through the intersection. Others said they crashed into the rear of the vehicle in front of them.
Many of the accidents were reported by drivers slowing down at an intersection or stop sign at speeds of 30 mph or less.
Warranty records show at least 6 percent of the vehicles' brakes were taken in for repair or replacement.
The government had been testing the brakes since March 1995. Agency officials complained it had been difficult to isolate any problem because brake failure was an intermittent problem that could not be readily duplicated by drivers.
According to safety administration documents, GM will attempt to rectify the problems with a safety recall of 1.1 million 1991-1996 Chevrolet and GMC four-wheel-drive sport utility vehicles and pickups equipped with "EBC4" brake units.
A defect relates to a braking system signal that normally tells it whether the vehicle is operating in two- or four-wheel-drive mode. If the vehicle is operating in two-wheel drive, the system wrongly believes it is in four-wheel mode, a condition that could extend stopping distance, according to the documents.
GM also plans to conduct a service recall of certain 1993-1996 light trucks equipped with the EBC4 unit. The automakers plans, at no charge, to modify a computer program governing the units on 1.4 million S and T light trucks and over 1 million 1992-1995 Chevrolet Astro Vans and GMC Safari Vans, and 1993-1996 G-vans.
"After considering all of the information developed during its extensive investigation, NHTSA has concluded that these two recall actions to be taken by GM will adequately resolve the issues raised by that investigation," one agency document said.
In two uly 1 letters to the safety administration, GM officials committed to the recalls.