Rep Power: 0

So I just recently purchased my first civic (second car) which is a 2005 EX Special Edition Coupe. I'm really happy with the way it drives and handles but recently the check engine light came on. I wasn't too worried about it because it didn't drive any different. I took it to AutoZone and they diagnosed it as a bad fuel cap. I've heard that's pretty common so I tightened the cap and drove it, as usual, hoping it would eventually go off. After a few days, it was still on so I got a new cap for 10$. Except the light is still on. Still drives really nice except I hate seeing that light. Also, the gas mileage hasn't been what I expected either. I live in a fairly hilly area and usually get just over 20 mpg city. Highway last time I checked was just over 30 mpg. I thought these cars got a lot better than that. I'm thinking maybe its a clogged fuel filter, fuel pump, and/or spark plugs. Any help would be appreciated.

 
Rep Power: 222

Get the actual code number Pxxxx format.
dont let AutoZone sell you anymore parts

 
Rep Power: 0

Code is P1456. EVAP system leak.

 
Rep Power: 222

Do you live in an area with winter that salts the roads?
Check under the car by the gas tank, you should see a back evap canister. It has a couple solenoids attached to it, if they look super rusty/crusty that probably your problem.
Hit them with some soapy water and see if you get bubbles

 
Rep Power: 0

I wouldnt think that it would be rusty but I havent checked. Im also in Florida so no salts or anything. With that code, does it definitely mean the problem is on the fill side, or could the problem be by the fuel pump?

 
Rep Power: 222

It's an evap problem (emissions) not a fuel delivery problem. Do you ever smell gas in or around the car? Sometimes the pump housing can crack and leak. There's an access panel underneath the rear seat, remove that and see if the top of the housing is cracked/wet

 
Rep Power: 0

Ok. I haven't smelled any gas but Ill double check that area. Ive seen videos on how to do that and it looks pretty quick and easy. Ill also check the EVAP purge control valve ( which I think is in the engine bay) and the EVAP canister for possible problems. Thanks for the help.

 
Rep Power: 0

So I checked the purge valve in the engine bay and it seemed to hold pressure fine. I also checked the evap control valve (attached to the charcoal canister) by connecting it to a 9 V battery and it clicked on and off. I think the only thing left to check is the charcoal canister. What kind of mpg decrease would I get from a bad charcoal canister? The ex se is rated for 38/31 and Im getting about 30/20.