Check engine code P0455 keeps coming on. I know it relates to EVAP system. Any help with problem,

njvolvo1

costs, estimated repairs, would be greatly appreciated

Mr_Shiftright

You might take a close look at your gas cap...check to see if the sealing gasket is old, brittle or cracked.

This code relates to some kind of leak in the EVAP system, or perhaps a malfunctioning valve, so it's hard to estimate the costs. A leak in the EVAP system is usually addressed using a smoke machine (because it's a vacuum leak so it will draw the smoke in at the point of leakage). Could be as easy as a loose or cracked hose. If you can locate your EVAP canister, you could examine the various hoses for looseness or cracking.

Here's a DISCUSSION about this code.