General Motors Corp.’s OnStar telematics and concierge service will make turn-by-turn navigation available to subscribers beginning next month.

The new system allows drivers to talk live to an OnStar advisor, who will send complete directions to the desired location through the vehicle’s OnStar system.

Audio directions are then relayed through the vehicle’s stereo system as needed. If the driver misses a turn, the instructions automatically update to get the vehicle back on course.

The navigation service integrates OnStar’s global positioning satellite technology with the vehicle’s antilock brake module for more precise positioning, GM says. The ABS module feeds data on differential wheel speed and directional information to OnStar, providing location fixes even in places where GPS satellites may have trouble pinpointing the vehicle, such as in dense urban areas and tunnels or near obstructions, the auto maker says.

On request, OnStar advisors also will provide subscribers with points of interest as part of the navigation service.

OnStar, which is announcing availability of the new service at the Chicago Auto Show today (Feb. 7), says OnStar Turn-by-Turn Navigation will be in place on about 1 million vehicles in the ’07 model year.

The service, which GM calls the highlight of OnStar’s new seventh-generation hardware, will bow as standard on ’06 Buick Lucerne and Cadillac DTS sedans in March and become standard on Cadillac STS sedans in second-quarter 2006.

It will be rolled out as standard on additional models equipped with ABS for the ’07 model year.

The service will be expanded further within the GM product portfolio in 2008, OnStar says.

OnStar recently passed the 4 million mark in active subscribers. (See related story: Now 10 Years Old, OnStar Appears on Firm Ground at GM )