My '01 4.2 has two codes up (with the check engine light)

P0491 and P0492.My hand held says "circ air bank 1 (and Bank 2)". My Bentley manual doesn't have this code on the list ??

Does anyone know what this means and how to go about fixing it. The car runs great except for the "Check Engine light".

 

Clear the code and see if they return.