A starting strategy for a power train of a motor vehicle including an internal combustion engine fitted with a drive shaft extending along a longitudinal axis, an alternator-starter, a first pulley that is designed to be driven in rotation by the drive shaft, a pulley that is rigidly connected to a shaft of the alternator-starter, a belt encircling said two pulleys, and a coupling/decoupling system between the first pulley and the drive shaft of the engine, characterized in that the starting strategy includes a preparation procedure for said belt in cold weather.