Found nothing specific with a search, and I can not be the only one to come across this. My 03' Automatic SE (71K miles) has been throwing SES codes “P0455 & P1448”. Gas tank pressure and an emmisions failure. I put in a locking gas cap back when gas was $3.40 per gallon, but had the cap for a good 4 months before the first SES code. I had the code reset and put in a new locking gas cap and it's back 2 weeks later. Both times it came up, was when the gas tank got down to about a 1/4 tank, so I still think it's gas cap related.

Has anyone run into this and found they had to go back to an OEM gas cap? Your input is appreciated... Thanks in advance.

 

You could have a legitimate failure with the evap canister and its leaking. The other issue maybe with where the filler cap screws in. On mine its very rusty preventing a tight seal. This weekend I took some sandpaper and tried to clean it up a bit. SES light is off now. Oh, put a piece of paper towel or rag in the hole to prevent crap from falling in the tank if you're going to do this.

 

Did the code go away on it's own or did you have it reset and it has stayed gone? I thought they had to be cleared by the portable unit?

Also, where is the evap canister and is it something that you can get to and replace yourself?

Thanks

 

I cleared the code myself using my code reader. You don't have to do this if the problem has really been resolved. The SES light will go off by itself if the problem is truly fixed after driving for a while.

I don't know about fixing the cannister itself. I haven't done it. You may not need to replace the whole cannister. There's a valve that has been known to go bad fairly often. You may just have to replace that. To determine exactly what needs to be done you need to do a smoke test. That will flush out where the system is leaking.

 

How do you perform this smoke test? Never heard of it. Where do you watch for the smoke, and where abouts is the canister location?

 

http://forums.maxima.org/showthread.php?t=452156

Mine had a crack in the canister at the vent valve mounting screw. In summary I ahd to replace both.

 

One other thing I noticed is that when I remove the gas cap to fill her up, there is no sound anymore of pressure relief. Does this point to a specific part failure?

 

Somewhere on here there is a link to a download Factory Service Manual for the 03 and others. This is great for diagnosing issues, a must have. I can't answer your gas cap question. I doubt there related as its not in the FSM.

 

OK.. Thanks All for the help and the links. I went out and looked at everything under the car, and everything looks OK (no cracks or detached hoses). When I have a chance, I'll take a closer look. Perhaps clean it up to expose hidden cracks, or even run the car and spray some soapy water under there. Perhaps that will expose a leak. I'll return and post my findings.

 

Remember its a vaccum test which failed and caused the SES. Its not going to blow bubbles like a tire leak. Best of luck.

It is simple enough to remove the assembly and check it. I never found the crack until I removed it. The FSM has a proceedure to check the parts.

 

Right! Dahhhhh... Don't mind me, it's Monday. I also just found out a friend can get me the FSM disk to borrow...