How do you change a Idler pulley on a Toyota Echo?

To change the idler pulley on a Toyota Echo, first, ensure the engine is off and cool. Remove the serpentine belt by loosening the tensioner pulley using a wrench or ratchet. Once the belt is removed, unbolt the old idler pulley from its mounting bracket and replace it with the new one. Reinstall the serpentine belt, ensuring it is correctly routed, and then check the tension before starting the engine.