Have you tried burning CDs with something than iTunes? Try, for example, the OS itself, or Disk Utility.
Secondly, the Pioneer may simply have a dirty laser lens. Buy a commercial cleaner disk and give that a go, or squirt compressed air from a can into the drive slot.
Next, the 109 is (relatively) an old drive. Pioneer are, in my view, the best optical drives for Mac but it may be that you need to think about upgrading your drive to a minimum 112D to accommodate the newer media (disk) technology.
G4 eMac 1.25 GHz, OS 10.4.11
G3 iMac 600, OS 10.3.9
G3 b/w 350, dual drives, dual OS, 10.3.9, 9.2.2
Numerous peripheral gadgets, all working.