To check if the pulley is at fault:
- Lift the bonnet
- With the car idling in neutral, turn the steering to full lock (either direction) and hold it there. An assistant doing this for you is preferable.
- Whilst doing the above, check the front of the engine bay, if you hear a flapping or screeching noise and can see the poly V belt vibrating, the pulley has failed.
It's common on all 1.9 TDIs.