I have a 1998 f150 with the 4.2 v6' the truck has about 850k miles, a few days ago the check engine light came on. I bring it to work to check it (advance auto parts) and here is what I get.

Code:
P0455
Evap emission system leak detected
(Gross leak / no flow)

-fix-
1- replace vapor management valve
(.Vmv)

I looked through my database and found nothing relevant.. any and all help or insight is greatly appreciated

 

Check your gas cap

 

mine had a hole in one of the lines on the side of the throttle body.

 

I actually just replaced all the vacuum lines and evap lines under the hood about 4 months ago, they were all brittle and dry-rotted.. however I don't think the light is attributed to that. I am thinking its an actual evap solenoid that has gone bad the only issue is there is the evap solenoid and there is the vapor valve, Both of which are expensive to replace and i dont like the 50/50 odds.

As far as the gas cap is concerned I am not entirely sure when or if it was last replaced it is still firmly attached with the factory leash which could mean that it is indeed the factory cap making it almost 14 years old, I will probably try that tomorrow.

My ultimate goal here was to catch wind of any possible alternatives or stories of people having success with the same code, I read through the few available threads about the P0455 code that I could find, and everything points back to the norm.

Thanks again for the help thus far, I will let you guys know my results with the gas cap.

 

Also gonna crawl under the truck on monday and see if i can see or hear any issues in the lines or filler neck.

 

850k miles? seriously?

 

The easiest way to find it other than hanging parts is with a smoke machine... visually inspect the lines on the evap canister to make sure they arent rotted as well.

I was hoping he meant 85k miles.

 

The zero was no typo it has to have atleast that... the odometer stopped in 2000 and my mom drove it that much and more for 8 years longer before I got it lol.. not entirely sure how its still rolling.

 

Had the same code, and a gas cap light come on. Bought a new cap from Ford ($23) and cleared light. All is good now. I recommend spending a couple of bucks on a good cap. And really crank it past the three clicks it recommends.

 

Test your gas cap 1st. It's the cheapest easy fix. If it was only a couple years old not suspect. On your code reader, navigate to freeze frame pages and document data, also navigate to I/M page and document test data. Periodically the system retests. If you have passed tests ( OK ) that system is good. If it is running a EVAP test and it is incomplete the Carbon Canister is suspect due to the control MALF code. You are at the "Canbus" network communication tests. A ford tech can help you or you can just replace the carbon canister as. There are valves in the system to insure no fuel vapors reach the air and the system holds psi. It has failed to pass the test due to a malf valve. You have to remove the spare tire to get to the Canister above and in front of it. You may find damage to it or a fault. Making sure all hoses are clamped is a good way to start, especially at the back of motor. Do normal maintenance like fuel filter and PCV valve + tube. ________________

Your code reader will give you a Ford PID ( perameter identification number ) It will greatly narrow down the fault area.