General Motors Corp. (GM) and Toyota Motor Co. (search) 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 (search).

Toyota's Lexus SC430 (search) 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. (search) 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. 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.

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, including handling, braking, engine trouble and vehicle design.

Automakers showed little improvement in overall quality in 2005, moving up just one notch from 119 problems per 100 vehicles in 2004.

GM's Hummer brand showed the most improvement from the 2004 survey, J.D. Power said. Hummer was last among vehicle brands in 2004 with 173 problems per 100 vehicles. This year, it had 110 problems per 100 vehicles.

Nissan Motor Co. (search) had the most improved vehicle model with the Nissan Quest minivan. The Kia Spectra, Hummer H2 and Toyota Scion xA also showed marked improvement.