A year after the hype began, automakers are struggling to work out the kinks

Apple Inc. sold 10 million units of the iPhone 6 and iPhone 6 Plus in their opening weekend last September and sold out of its latest gadget, the Apple Watch, before it even arrived in stores.

But a year after Apple's splashy unveiling of CarPlay, a system for controlling a phone's functions through a car's display screen, the number of cars sold with the technology can be measured in the dozens, not the millions. Apple said its rollout would begin in 2014 with Ferrari, Mercedes-Benz and Volvo, but so far, only the $198,973 Ferrari California T and the $295,000 Ferrari FF have shipped with CarPlay on board.

Like rival Google Inc., Apple is finding that reconciling the rapid-fire renewal of smartphone technology with the auto industry's more deliberate, risk-averse approach isn't so easy.

"I don't think either Apple or Google fully understood the complexities and the stringent reliability requirements that would be necessary to launch a technology like this in a production vehicle," said Mark Boyadjis, a senior analyst at the consulting firm IHS Automotive. "There was a lot of initial hype, and people thought this would move forward at the speed of mobile devices, but it's still a car technology."

Mercedes-Benz, the second of Apple's three partners, has yet to offer CarPlay in any of its vehicles. And Volvo, which saw CarPlay as a way to burnish the high-tech credentials of its redesigned XC90, has started shipping the crossover without CarPlay on board.

U.S. deliveries of the XC90 will begin in May, but CarPlay is not expected to become available until November, Volvo spokesman Jim Nichols wrote in an email. At that point, owners would be able to return to the dealership for a software update. Volvo wouldn't comment on the reason for the delay.

Google has encountered similar hiccups in the introduction of its system, Android Auto, which, like CarPlay, enables users to access maps, music and messages from a smartphone using a car's built-in touch-screen display and voice controls.

Hyundai has raced to be first to market with Android Auto, declaring that it would be available in the 2015 Sonata. With the 2016 model year close at hand, Hyundai promised on Twitter this month that Android Auto would be available soon.

Hyundai spokesman Miles Johnson said the automaker intends to make a running change on its assembly line in Montgomery, Ala., so remaining 2015 Sonatas can be sold with Android Auto. He said Hyundai also will put the software online so dealers can load it onto a USB drive and update their inventories.

Johnson said the delay is the result of validation testing. Smartphones are easily updated over the air, but few cars have that capability, so automakers are determined to defeat as many bugs as possible before they ship a car with the technology.

During one recent testing session, Hyundai's engineers pressed the voice control button several dozen times, then unplugged the smartphone and plugged it back in. The car's screen went black for a while before returning to a colorful home screen.

"If you have a black screen of death where the thing's not working, you've got a real problem on your hands," Johnson said. "Hyundai's not going to put anything out unless it's perfect."

Legal questions also have slowed the adoption of CarPlay and Android Auto.

Apple and Google see their systems as a remedy for distracted driving. Yet the new interfaces could prompt lawsuits if they come to be perceived as dangerous, and automakers likely would bear the brunt of that legal exposure.

"Liability goes to whoever's logo is on the steering wheel," Boyadjis said.

Some automakers have asked Apple and Google to accept a portion of this risk, as traditional automotive suppliers do, said a source from an automaker familiar with the ongoing negotiations.

"We want some sharing of liability," said the source, who asked not to be identified because he hadn't been given permission to discuss the negotiations. "They want no liability."

Apple and Google both declined to comment on legal matters.

Whatever terms car companies set for their relationships with Apple and Google will set an important precedent, said David Strickland, the former administrator of the National Highway Traffic Safety Administration who now consults with the industry as an attorney at Venable LLP. A deal struck today could become the norm for future dealings with Apple and Google, and if car companies deviate from usual policies to accommodate Apple and Google, other suppliers may ask for the same treatment.

"The manufacturers," Strickland said, "have to play chess five moves ahead."

Apple and Google have signaled they are happy with uptake of CarPlay and Android Auto. More than 40 car models will ship with CarPlay by the end of this year, Apple CEO Tim Cook said last month at an event here.

"It's unbelievable momentum," Cook said.

Apple hasn't identified these models. Most automakers have kept mum. Honda, Acura and Volkswagen all say they will offer both systems in 2015, but they have not announced in which models they will appear.

Kia has tapped the 2016 Optima, which goes on sale this fall, as its first model to offer Android Auto and CarPlay. Audi is expected to launch them with the redesigned A4, which arrives in U.S. showrooms in early 2016.

Ford built its new Sync 3 infotainment system to support Android Auto and CarPlay. Some cars may be sold before Android Auto and CarPlay are ready, a Ford spokesman said, but they could get the software later using the car's Wi-Fi connection.

IHS projects that 800,000 vehicles will be sold globally with CarPlay in 2015, rising to 3.2 million in 2016, while Android Auto will ship in 600,000 vehicles in 2015 and 3.1 million in 2016. Most vehicles equipped with one system also will have the other.

Audi spokesman Brad Stertz said the company's launch of CarPlay and Android Auto remains on schedule. Audi never intended to be first to market, he said, because CarPlay and Android Auto were designed for touch screens, and the rotating **** and touchpad used for Audi's MMI interface had to be reprogrammed to work with them.

"We're right where we thought we would be," Stertz said. "Customers want it right now, of course, but there's more re-engineering that has to be done."

What's taking so long?

So far, just a few Ferraris have been sold with Apple CarPlay on board. Hyundai declared the 2015 Sonata would be available with Android Auto, but it has been delayed. Here are 3 reasons the systems are taking longer to materialize than hoped.

1. Validation testing: Some companies, such as Hyundai, have built cars to run on Android Auto and CarPlay but waited to activate the software to squash bugs.

2. Legal questions: Automakers bear legal liability for whatever goes wrong. Some are asking Apple and Google to share a portion of the risk.

3. Controller compatibility: Luxury brands that use ***** and touchpads need time to re-engineer these controllers to work with CarPlay and Android Auto.

Apple CarPlayŽ takes the things you want to do with your iPhone while driving and puts them right on your car’s built-in display. You can get directions, make calls, send and receive messages, and listen to music right from the touchscreen or by voice via Siri. Supported apps include Phone, Messages, Maps, Music and compatible third party apps. Apple CarPlayŽ is compatible with iOS 7.1 or later and iPhone 5 or later.