Just replacing the pulley on the tensioner will not solve your problem. You will need to replace the entire tensioner assembly. Mine was replaced under warranty last month. Check with Rock Auto or Advance Auto Parts for the tensioner assembly. To remove the tensioner assembly you will need to jack up the passenger side of the engine to get the bolt out once it is loose. Not a simple job, unfortunately.
My Fleet:
'15 Ford Fusion AWD Titanium 2.0 Tutbo
'14 Lincoln MXZ AWD 2.0 Turbo
'14 Nissan Pathfinder AWD SL
'05 Pontiac Vibe AWD