Hoping to boost its residual car values, General Motors Corp. extends its 5-year, 100,000-mile (160,934 km) powertain warranty to certified used vehicles.

Certified used vehicles from Buick, Chevrolet, GMC, Pontiac and the now defunct Oldsmobile will get the extra protection. The warranty will cover ’02-’06 models and does not require deductibles.

The used-car program starts in March.

GM introduced the 5-year, 100,000-mile warranty this fall to cover ’07 models in an effort to boost consumer confidence in its vehicles.

Powertrain warranties generally cover mechanical components such as the engine and transmission.

GM says Saturn is expected to announce a similar program later this year, while Cadillac, Saab and Hummer pre-owned models already carry a 6-year/100,000-mile bumper-to-bumper limited warranty.

At the same time, GM is adding auto website Cars.com to its online listings program. Partnering with Cars.com will double its Internet vehicle listing footprint, GM says.