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I have been working on a 2002 F150 with a 5.4L motor. I have been able to fix the lean codes I was getting. After 74 mile on the trip meter I got a dash light (not a check engine light) I didn't know what it was so I did a Google lens image and it was a warning for the gas cap. I replaced the gas cap since the truck has 281xxx miles on it. I cleared the codes and drove it another 123 mile then the check engine light came on, P0455.
Grrr. I was going to go get a Smog check that day since I am in CA and then check engine light.
I watched some videos on the P0455 EVAP code and took off the purge valve to see if I can blow air through it. Blowing from the charcoal canister side when removed from the truck I can definitely blow air through it. From what I researched this is a stuck open purge valve and is bad.
Does this seem to be correct?
Thanks
Update
I got out the volt meter and did some testing. Alligator clips to the 2 pin and Ohms testing and read .0
I went to Pick n Pull and found a couple trucks with purge valves and tested those and got a few of the same readings .310 ( I don't remember where the decimal was )
So I bought one and installed it. I have driven the truck over 100 miles and no check engine light. This morning I ran the smog check on my Blue Driver scan tool and it looks like it is read for state testing. Fingers crossed.
The purge valve must have been stuck open to throw a P0455 code
Last edited by teamjnz; Oct 29, 2025 at 03:32 PM.
Reason: added info
another update
Well the truck threw another P0455 code after 154 miles. This is getting old!
I figured out how to get my smoke machine attached to the fuel filler with a plumbing flexible 2 inch coupler. So I was able to attach the smoke machine. I was thinking it was going to be the filler hose or the venter hose after the metal filler neck. The truck is lifted like a 4x4, but is a 4x2, so I was able to stick my head in the wheel well and I smelt gas so I was convinced it was one of those old hoses.
After the smoke machine was running for a little while I got under the truck and saw smoke coming from the top of the tank. I couldn't quite see where so I had to lower the fuel tank a about 6-8 inches and saw where the smoke was coming from. The FUEL PUMP not the hoses. There is a plastic unit with an o-ring that seals the electrical wirers that go into the the pump. This was came out and was loose. I was able to press it back down so the o-ring is now sealing.
I let the smoke machine run a while longer and didn't see any smoke leaks or smelling fuel. Fingers crossed this is the fix.
BTW, that green cap on the purge valve is provided so that you can connect your smoke machine (or other appropriate tool) directly to the evap system. That way, you can also test the seal of the fuel cap.
BTW, that green cap on the purge valve is provided so that you can connect your smoke machine (or other appropriate tool) directly to the evap system. That way, you can also test the seal of the fuel cap.
