DETROIT ? General Motors Corp. and Toyota Motor Co., the world’s two largest automakers, had the top vehicles in 15 of 18 categories in a closely watched survey of 2005 models released Wednesday by research firm J.D. Power and Associates.

Toyota’s Lexus SC430 was the highest-ranking vehicle for the second year in a row. Owners of the luxury sedan reported 54 problems per 100 vehicles, less than half the industry average of 118 problems per 100 vehicles.

Suzuki Motor Corp. had the highest rate of problems per vehicle at 151 per 100 vehicles.

Overall, Toyota had the top vehicles for initial quality in 10 categories, including the Toyota Prius compact car, Toyota Sienna minivan and Lexus sedans in all three luxury car categories. Toyota said that was a record number of segment awards in the study.

GM had five winners, including the Buick LeSabre full-size car, Chevrolet Suburban full-size sport utility vehicle and GMC Sierra heavy-duty full-size pickup. That was a boost for the automaker, which saw its U.S. vehicle sales fall 7.7 percent in the first four months of this year.

The survey, in its 19th year, is an important one for automakers, which often use the results in their marketing campaigns. J.D. Power and Associates questioned more than 62,000 people within 90 days of buying or leasing a 2005 vehicle. The survey measures 135 attributes, from handling, braking and engine trouble to seat comfort and stereo systems.

GM’s Hummer showed the most improvement from the 2004 survey. Hummer was last among brands in 2004 with 173 problems per 100 vehicles. This year, it had 110 problems.

While some automakers note that new car models often are prone to prone to problems and consumer complaints, Oddes disagreed. The new 2005 Hyundai Tucson, for example, had just 99 problems per 100 vehicles.

“Hyundai is truly dedicated to making a quality product,” said Neal Oddes, J.D. Power’s director of product research.