2006 hyundai accent, trouble code P0455 What is problem and the solution?

SOURCE: 2000 Hyundai Accent GL check engine

i just replaced the timing belt, and asked the garage to look at the transmission for me because i thought i was experiencing some subtle shifting problems. they told me the transmission looked fine, but i needed a new filter and fluid. the engine light didnt turn on til a couple weeks later tho. does this sound like a new filter and fluid would fix this problem?

SOURCE: My 2006 Accent is idling high

the tps (throttle position sensor) could be causing the problem

SOURCE: 1999 Hyundai Accent trouble code P0343

camshaft position sensor high input,check sensor,if out of spec,replace

SOURCE: 2000 hyundai

It sounds like the fuel pump is getting a bit weak, and when you remove the filler cap, this relieves pressure within the fuel tank. A good local mechanic should be able to quickly test the fuel pressure generated by the fuel pump. Many auto parts stores sell a fuel pump pressure tester. But working with fuel lines and raw fuel isn't a good idea unless you know what you are doing. It could be the fuel pressure regulator valve, but this is less likely.

Possibly your engine could have a serious vacuum leak somewhere on its intake side of the engine, but you would have other symptoms aside from the specific symptom of having difficulty starting the car after filling the car up with gas.

It occurs to me that the following test might indicate a failing fuel pump:

After driving for a while (at least 10 minutes), turn off the car, then take the gas cap off to relieve tank pressure, put the cap back on, and then see if you have difficulty starting the car. If you do, then a failing fuel pump is the problem. Well, at least if this test confirms the problem, its better than suddenly being stranded when the fuel pump does completely give up the ghost! :-)

SOURCE: trying to find the fuel filter in a 2006 Hyundai Accent

YEP! It's in the fuel tank at the bottom of the fuel pump... it's called a 'SOCK.'