Alan03MB

Good Afternoon.

I have a 2007 S550 that for the last year has had The P2421 and P2422 Codes.

I have replaced both evap valves (under the hood and on the Charcoal Canister)as well as the fuel cap which got rid of the codes for about 1K miles but the ultimately came back. I do not have fueling issues as it is indicating that the valves are stuck open.

I have a replacement canister that is scheduled to be delivered tomorrow.

I am just wondering if there is anything else I should be checking, or if anything else could be the problem.

Thanks in advance

vchris11

My 2007 R350 Mercedes check engine light code P2421,,, Canister vent valve stuck open permanently, I checked connection for 12v, it's good replaced vent valve. Clear code, light back on, replaced Purge valve, gas cap, hoses,,, check engine light still showing up, so I got tire of clearing the code and determine to find the problem so I purchased a smoke machine for $120 and where the that was causing the P2421 code and the problem was around my fuel pump locking ring or the cap that holds the fuel pump in place...when I did the smoke test through my purge valve line, smoke was just pouring out around the fuel pump cap...now I know why I was smelling fumes... I purchased new fuel pump locking ring with gasket... problem solved

WRC-LVR

Great post, right to the point and shows the real fix for the issue. Good on you !!!!