P0452 OBD2 code?

[flyboy1294]

Hey guys,

Over the past few months, I have noticed my engine light coming on periodically. One by one I have tracked down the individual causes and fixed them. It was never anything too bad, just little stuff like bad 02 sensors, cracks in vacuum hoses, etc.

Anyway, lately I have had the light coming on randomly after 100 miles ish. It never comes on when the truck is running. I will turn it off, and when I got back to start it sometimes it will be on. It also will go off on its own after 50 miles or so. I will go back to start it and it will be off. This has been going on for a few weeks, and I have never had the light on when I was near anyone with a scan tool so it normally slipped my mind. Well today I had the chance to get the error code read. It comes back as PO452 which is apparently low EVAP pressure.

Any ideas what could be causing this? I don't believe it is a big deal since it comes and goes, but it is annoying after awhile. I appreciate any help.

 

[Aloicious]

tighten your gas cap...EVAP pressure is read at the tank...it may be time for a new gas cap if the gasket on it is starting to go and not seal as well.

 

[kn1ght]

When you get gas, make sure you turn off your truck as well. It's almost always a gas cap issue.

 

[flyboy1294]

When you get gas, make sure you turn off your truck as well. It's almost always a gas cap issue.

I always fuel up with the truck off.

tighten your gas cap...EVAP pressure is read at the tank...it may be time for a new gas cap if the gasket on it is starting to go and not seal as well.

Hmm. I normally turn the cap until it clicks. I will turn it until it clicks a lot and if it doesn't get better I will go from there.

 

[Aloicious]

yeah, it could be that rubber gasket getting old and not sealing correctly. you might just need a new gas cap...

the code you're getting is indicating that the fuel vapors from the tank are leaking out somewhere, not to the EVAP canister. its 99% of the time from the gas cap.

 

[kn1ght]

And unless the light drives you crazy or you need it off to pass emissions, it doesn't hurt a thing.

 

[Aloicious]

yeah. personally the light would drive me insane....

 

[kn1ght]

Mine camaro used to do that, but when we took all the gay emissions junk off, and converted it to a carb, it never went off, so I pulled the dash apart and solved my problem with a black sharpie. lol.

 

[Aloicious]

'eh, the problem with that is that the SES light is very useful, it does help indicate when some problems arise long before they can be felt/heard/etc, so I'm not a fan of leaving it on, or blacking it out, etc...some of the codes like the gas cap stuff are annoying, but there are many things that the SES can indicate before you have a physical problem. personally, since I have the ability to tune my PCM, I prefer to just turn the less-useful codes off, but leave the majority of them functioning.

also, pre-98 trucks won't get the gas cap code, because there is no EVAP pressure sensor used in the GMT400 until 98.

 

[DRAGGIN95]

'eh, the problem with that is that the SES light is very useful, it does help indicate when some problems arise long before they can be felt/heard/etc, so I'm not a fan of leaving it on, or blacking it out, etc...some of the codes like the gas cap stuff are annoying, but there are many things that the SES can indicate before you have a physical problem. personally, since I have the ability to tune my PCM, I prefer to just turn the less-useful codes off, but leave the majority of them functioning.

also, pre-98 trucks won't get the gas cap code, because there is no EVAP pressure sensor used in the GMT400 until 98.

Word, I will keep my EFI and ecm over a carb setup any day!