I am not sure if the problem really exist. The resulting diagnosis is based on a faint whine detected by the technician and a determination can only be made by a physical examination of the timing guide. To do this would require removing parts. But when those parts are removed the guide and chain will need replacing even if they are not defective. Nissan has known about the problem dating back to the 2004 model and no definitive diagnostic method is available that will not cost the owner a repair that is some times unnecessary.