Use this diagram for the 2001-2005 Impala, Regal, Monte Carlo, Century, Grand Prix, Intrigue and Lumina.

Rotate the Tensioner releasing tension on the belt and remove it. Inspect all your pulleys and make they are clean and there is no debris or fluids on them.

Route the belt according the diagram leaving the tensioner for last. Rotate your tensioner and slip the belt back on. Inspect the belt again to make sure it is aligned correctly on each pulley. The tensioner can be rotated a little to give it slack if you need to make adjustments.