The JD Power survey is much more limited in scope than what’s available from Consumer Reports:
http://www.consumerreports.org/cro/2011/12/consumer-reports-car-reliability-faq/index.htm#1.2
The timeframes used in collecting data also differ among surveys. J.D. Power’s IQS is based on the first 90 days of ownership of new vehicles only, and its VDS (Vehicle Dependability Study) is exclusively based on 3-year-old vehicles. CR’s survey asks about subscribers’ experiences with their vehicles over the course of the previous 12 months and, starting with 2006, CR’s survey now covers 10 model years—from brand-new models to models that are 10 years old, providing a more complete profile of the life of a model. Our Predicted Reliability, which forecasts how well a new model is likely to hold up, is based on the cumulative experiences of owners of the three latest model years.
Consumer Reports has been in the bag for Japanese car makers for years.