Hey guys, I've got a check engine light coming on in my 2001 5.4 crew cab f150. Ive done a pretty good amount of research about these codes and found that most were solved with a new PCV hose and a few others with mass air meter cleaning etc...

well on my truck. the PCV hose was fine, but i replaced it anyway.. cleaned the mass air meter, checked for cracked vac. hoses etc.. new fuel filter also.

after doing these few things I, still getting the light back on after about 75-100 miles.. Any more ideas?

now for my evap, the truck is due for a smog but I need to get the monitors for the OBD II to reset. but I cant get the EVAP and the Cat. converter to set. but all the rest will.. some Im wondering if the check engine light is in somehow messing with the Cat. monitor. the EVAP im lost on.. been driving the truck with between 3/4 and 1/4 tank and it will not reset.. each time I take the cap off the tank will hiss so I know its holding pressure but Im lost at this point..

Thanks for your insight guys...

 

The P0171/174 are from unmetered air entering after the MAF. While the PCV elbow is the most common thing, there are a bunch of other things that can cause it too.
Almost any vac hose
Brake booster line
Bad brake booster
Leaking intake gaskets
The tube from the air cleaner being loose or cracked
Exhaust leaks near the O2 sensors
Cracked exhaust manifold (usually only 1 side shows bad)
I have even heard of a bad rocker cover gasket causing it.
Cracked vac reservior (the black thingie by the battery)

Start by replacing/checking ALL the vac lines, go cheap and work your way up from there.


The EVAP takes the longest to reset, and every time you clear the codes the drive cycle has to start over. Most states will allow 1 or 2 monitors to show not ready and still pass.

What is the EVAP code you have "P" number?

Good luck and welcome to the site.

 

Check out this link for P0171 and P0174. These codes are discussed in the TSB.

http://www.v8sho.com/SHO/TSB0197HO2SServiceTips.htm

Good Luck

 

Thanks guys.. I'll keep looking around, I should also say I have no drivability issues or rough idle or anything..

 

The truck only has the two codes.. No evap codes it just will not reset..

 

Not sure if the 5.4L is like the 4.2L V6, but those codes will pop if the isolation seals under the intake manifolds are leaking. It shows up about 70,000 miles when the plastic assembly warps some. Everything you'd think it would be gets replaced and that is the last thing to replace. It went on my 2001 F150 and my son's. We both had 4.2L V6's however. It is a bit of a job to replace, but I hear it is very common.

 

The evap monitor won't run if you have those codes. You need to resolve the "lean" codes or it will automatically fail due to the MIL.

Most jurisdictions will permit one or two incomplete monitors and still pass. Check with your local testing authority for your rules. You may be beating your head against the wrong wall.

 

Thanks guys.. Still trying to fix this issue but no luck yet.. I'm aloud to have one unset monitor here in CA. So something's got to get fixed.. Is there a good way to test if the manifold isn't sealing right?

 

Alright.. So while I was laying under the truck and trying to find any leaks I might have missed I did happen to notice that my dr. Side cats were making some noise so I turned the truck off and started hitting the cats and u could hear stuff bouncing around inside of there. But I'm wondering if the cats are any good on the passenger side?? Anybody think the cats could cause this issue I'm having?

 

No.

 

Anymore insight guys? Can't figure this issue out?

 

Check EGR, and IAC components. If no go there, used brake cleaner to spray test for vacum leaks. Make sure to check around intake manifold as well. I was getting these codes, and replaced EGR, PCV, IAC and lines with no luck. Ended up being cracked intake manifold. Replaced it and codes are gone. I was also getting a whistling sound.