The survey of dependability of 2013 models by J.D. Power found owners reported twice as many complaints about pairing a smart phone with a vehicle’s communications system as issues with engines or transmissions.

The finding—and the attendant lack of confidence on the part of owners—indicated the country is not yet ready for widespread use of self-driving cars, J.D. Power suggested.

“While automakers, suppliers and even the U.S. government are enthusiastically moving toward putting fully autonomous vehicles on the roads, consumers need to have confidence in the technologies currently in vehicles before they will be willing to take their hands off the wheel of self-driving cars,” J.D. Power said in a news release.

“If consumers can’t rely on their vehicle to connect to their smartphone, or have faith that their navigation system will route them to their destination, they’re certainly not yet ready to trust that autonomous technology will keep their vehicle out of the ditch,” said Renee Stephens of J.D. Power.

In terms of brand dependability, owners of Lexus, Toyota Motor Corp’s luxury brand, reported the fewest problems among 32 brands. It was the fifth consecutive year that Lexus topped the J.D. Power “Vehicle Dependability Study.”

Porsche, a sports car luxury brand of Volkswagen AG was second, followed by General Motors Co’s (GM) Buick and Toyota’s namesake brand.

GM brands did best among mass market vehicles, as GMC was fifth and Chevrolet sixth. GM’s luxury Cadillac brand was 15th, just above the industry average for number of problems reported by respondents.

Audi, VW’s primary luxury brand, was 11th in the study after getting top honors in the Consumer Reports survey for vehicle quality issued on Tuesday.

Subaru, a unit of Fuji Heavy Industries, was 23rd in the J.D. Power study after being second in the Consumer Reports study, in which Lexus was third.

At the bottom of the J.D. Power study was Dodge, a Fiat Chrysler Automobiles (FCAU) brand, and Ford Motor Co’s (F) namesake brand was next-to-last.

The annual study, now in its 27th year, complements one that addresses initial quality that J.D. Power issues after surveying owners after 90 days of ownership.

For more on the study, go to http://www.jdpower.com/resource/us-vehicle-dependability-study.