Dealer changed mine, but I had some squealing that I solved with a very precise application of some Silicone Lube. I sprayed both idlers and the sound went away.
One idler is on the right hand side of the motor between the crankshaft pulley and the power steering pump. It has a cap that keeps stuff off the bearing - you need to spray behind that cap.
The other idler is built the same, and is just beside the alternator. Don't try spritzing this one while the engine is running, the cooling fan is too close and doesn't care about removing chunks from your hand.