| Investigations Summary:
This investigation was opened on Mar. 30, 2010.
It was closed on Jan. 5, 2011.
The office of defects investigation (odi) received defect petition dp10-003 on March 2, 2010, requesting the investigation of model year (my) 2003 Chevrolet silverado 2500hd 4wd pickup trucks for corrosion failures of the vehicle brake lines. Dp10-003 was granted and on March 30, 2010, preliminary evaluation pe10-010 was opened on more than six million model year 1999 through 2003 light trucks and sport utility vehicles manufactured and sold by general motors corporation (gm). On July 2, 2010, odi received gm's response to an information request, which included gm's assessment of the frequency and safety consequences of the alleged defect. Gm stated that:(1) the brake system of the subject vehicles is split front/rear and should a brake pipe suddenly fail for any reason, the affected vehicle would be capable of stopping with the pressure supplied by the remaining circuit; (2) the subject vehicles were designed to meet the hydraulic circuit partial failure requirements of federal motor vehicle safety standards 105 and 135, light vehicle brake systems; and (3) should a brake fluid leak occur for any reason, the brake system malfunction indicator lamp (mil) would illuminate and warn the driver before the brake fluid level was low enough to cause a loss of line pressure. Odi's and gm's analysis indicates that 85 percent of the complaints occurred on vehicles used primarily in states that use salt on the roads during winter months (connecticut, delaware, district of columbia, illinois, indiana, iowa, maine, maryland, massachusetts, michigan, minnesota, missouri, new hampshire, new jersey, new york, ohio, pennsylvania, rhode island, vermont, west virginia and wisconsin). Overall the complaint rates per 100,000 vehicles for salt belt states is 43. 0 and non-salt belt is 3. 0. In approximately 25 percent of the complaints the brake pipe failure occurred suddenly, with no warning (I. E. , no mil, brake fluid loss warning), and resulted in extended stopping distances. In 30 of these the increase in stopping distance that resulted was a factor in the crash and in 10 others the vehicle was intentionally steered off the road or into another lane of travel in order to avoid a crash. This investigation has been upgraded to an engineering analysis (ea11-001) for subject vehicles sold or currently registered in salt belt states to further assess the scope, frequency and safety risks associated with sudden failures of corroded brake pipes that can result in decreased brake effectiveness. Odi will continue to gather information on subject vehicles outside the salt belt as well.