Originally Posted by WVMIKE
Both of my Evap Codes ARE! P1456 and a 0442! Please chime and there ya go!
I fought with both of these codes for a long while before I got it sorted out. First tried a new OEM gas cap with fingers crossed and that didn't help.
Read about a recall for the fuel sending unit due to corrosion. I bought hte truck used, looked it up and it hadn't been done yet so got that done - they did a new gas tank along with it. That got rid of the P0442 for the most part, but it did return from time to time although few and far between.
All the lines under the truck seemed good and the canister was replaced recently by the previous owner so I knew that wasn't it.
Got to under the hood and found some sketcky connections on the evap lines on a valve located on the driver's side fender.
Replaced the lines and the P0442 was gone for good, P1456 would return only after the truck had warmed up ona longer drive. I knew I was getting closer...
Re-examined the valve itself on the vender and one of the connection nipples appeared to have a hairline crack in it. Replaced the valve itself and both codes are gone.
For me it was a combination of gas tank (was rusted on the top near one of the nipples and had a pin-hole leak) and the evap valve on the driver's fender.