I have several check engine codes that i have my mechanic...

I have several check engine codes that i have my mechanic keep checking. He said it was the gas cap but it came back again. Then he said it was the fuel tank pressure sensor. It came back again and I think he is throwing me for a ...

I have several check engine codes that i have my mechanic keep checking. He said it was the gas cap but it came back again. Then he said it was the fuel tank pressure sensor. It came back again and I think he is throwing me for a loop so I checked the codes myself. It's a P0451 and p0455 code. What is wrong? I need to pass inspection it was due last month! Mechanic's Assistant: Are you certain it's the fuel pressure sensor that's in need of attention? What about the fuel rail? Have you checked it yet? He said he replaced the sensor but the code came back. I don't know about the fuel rail Mechanic's Assistant: What is the make/model/year of your car? Hyundai sonata 2011 or 2012 I keep forgetting sorry Mechanic's Assistant: Are you fixing your Sonata yourself? What have you tried so far? I gave it to the guy that sold me the car, whose my mechanic, but he hasn't fixed it yet. All I tried doing was using a computer to clear the codes. Mechanic's Assistant: Anything else you want the Mechanic to know before I connect you? Yeah it has 160k miles on it but still in excellent condition other than the check engine that keeps coming up