GM Service Manual Online
For 1990-2009 cars only

If the vehicle has this feature, engine power is sent to all four wheels when extra traction is needed. This is like four-wheel drive, but there is no separate lever or switch to engage or disengage the front axle. It is fully automatic, and adjusts itself as needed for road conditions.

If the vehicle is a Two-mode Hybrid, see "Four-Wheel Drive" in the Two-mode Hybrid Supplement.