Hi all,

So I just had these two codes pop up over the last few days on my 2003 W211 E320. The P0456 one has been an intermittent code over the last month, but this morning when I went to AutoZone to have the codes read, they also got a P0446 from the diagnostic port.

I tried replacing the gas cap with an OEM one from the dealer, as that seemed to be the most common way to address P0456, but it looks like the problem is getting worse with that additional code.

A few questions:
1) The car doesn't seem to be driving any differently at all (though my fuel efficiency does look to be much worse), is it necessary to fix this? If I don't will it cause more damage?
2) Any troubleshooting steps you guys can recommend to see what's going on? I tried to call the dealer to ask about if this could be related to the fuel sender warranty extension, and she gave me the run-around about not diagnosing it without taking it into the shop. Ideally, I'd like to get some better idea what's going on here, before taking the plunge one way or another on it.

Thanks so much for all your help!

 

Evap leak. MOT valve, or purge valve. Fuel tank leak test will tell you exactly how much pressure loss in your evap system is being drawn. DAS/Xentry is what ya need.

 

I know it's old, but these codes are for the canister purge valve. Easy fix.

 

If you smell any fuel inside car, or see any by raising rear seat cushion, and inspecting fuel pump and sending unit, this could be covered under extended 15-year warranty. Do you smell any gas after you've gotten a full tank, especially coming out of rear left wheel well?

Extended warranty will cover you if any fuel is smelled due to a leak.