How do you change tensioner pulley on peugeot 307 2.0 d turbo?

To change the tensioner pulley on a Peugeot 307 2.0 HDi turbo, first, disconnect the battery and remove any components obstructing access to the serpentine belt. Release the tension on the belt using a suitable tool to turn the tensioner pulley clockwise, then carefully remove the belt. Unbolt the old tensioner pulley from its mounting, replace it with the new pulley, and reassemble everything by reversing the steps. Finally, ensure the belt is properly routed and tensioned before reconnecting the battery and starting the engine.