DETROIT – Starting this month, if you crash a Cadillac SLS into The Great Wall of China, OnStar will dispatch aid.

OnStar executives confirm the Chinese-market rollout of its concierge service in the crest-and-wreath brand’s fullsize luxury sedan. And OnStar’s hands-free calling service will offer voice recognition in Mandarin, which is no mean feat: the Asian language is regarded among the most difficult to discern with software.

“It has a lot of tones,” explains Nan Ratner, chair of the University of Maryland’s hearing and speech department.

OnStar’s voice-recognition software breaks down words by syllable. But in Mandarin, “a single syllable can have many tones associated with it,” Ratner says, adding the language also features a high percentage of “soft” syllables.

Such syllables include those that begin with the sound made by the letter ‘s’, which can be difficult to decipher.

Accordingly, engineers spent countless man-hours to make Mandarin the fourth language accommodated by OnStar. The others are English, Spanish and French.

Noting OnStar’s 14-year history with speech-recognition software, Tony DiSalle, vice president-sales, service and marketing, says a breakthrough was inevitable. “We’ve been living with it,” he says of the technology.

OnStar’s entry to the world’s fastest-growing light-vehicle market is the result of a joint venture with Shanghai General Motors Co. Ltd. and Shanghai Automotive Industry Sales Corp.

Meanwhile, OnStar – which currently is exclusive to General Motors Co. brands – is “talking with other car makers,” says Nick Pudar, vice president-planning and business development. But Pudar is mum on progress.

OnStar’s potential customer base is squeezed by GM’s decision to jettison its Saturn, Saab, Hummer and Pontiac brands, a dynamic compounded by industry sales which slumped to an annualized rate of 10.29 million units through November, down from 13.51 million in like-2008.

OnStar, which does not disclose its subscription renewal rate in actual numbers, has acknowledged about two-thirds of GM customers stay with the service after their 1-year trial period ends.

Says OnStar President Walt Dorfstatter: “It’s not an easy message to tell in a 30-second spot. But we’re passionate about it. We know we’re doing the right thing and helping a lot of people.”

Every month, the service handles about 2,300 crash notifications, 10,000 emergency calls, 500 stolen-vehicle reports, 53,000 requests to remotely unlock doors and 27,000 roadside assistance calls.

Notable are an additional 6,300 “Good Samaritan” events in which OnStar subscribers witness emergencies and intervene by calling the service. “Our subscribers are very, very happy to help others,” Dorfstatter says.

Some 3.6 million vehicle-diagnostic reports also are sent to customers via OnStar every month. An additional 48,000 on-demand requests are received from subscribers who have questions about their vehicles’ performance.

And the service’s hands-free calling function accounts for more than 26 million minutes every month.