I got downtime to work on the system. Needless to say, never having worked on a R900, I was quite happy to see that Dell has made system maintenance easier on the newer models. Getting to the Fan Power Distribution Board required disassembly of most of the system. Since I had to pull the Power Distribution Interposer Board to be able to change the Fan Power Distribution Board I decided it would be a good idea to replace both of them at the same time. It has now been over a week since replacing these parts and we have not had any Fan 2 errors. I a not sure what actually fixed the problem, however the customer and I am happy that it is resolved. Robert, thank you for all the help you provided.
 I am receiveing an error message indicating that Fan 2's speed  is dropping. I am attempting do identify which of the four front fans is Fan 2.
Poweredge R900 System Fan identification.