new to the forum.. questions already.. check engine light

The first thing i'd do is test the canister vent shut valve.

ill get right on that... but i have no clue what that is or how to test it or what to look for... i am DIY guy but im use to working on pre 1975 cars so this aint my strong hold

Welcome to the site.  I can't help with the diagnosis, but welcome anyway.

ok so i have had my car look at.. and there are no leaks or anything like that. they did a diagnosis... and of the 20 odd things they had to check everything passed except two possible reasons why im pulling the P1457 code. so its either my fuel tank pressure sensor is malfunctioning or my cars computer sysytem is malfunctioning. so i have a question i no what the ECU is but what is the ECM and PCM are they the same thing or is each something different?

Those are sorta the same thing.
 
ECU = engine control unit (Honda doesn't use this term, but it's common with European carmakers)
 
ECM = engine control module
TCM = transmission control module
 
PCM = powertrain control module = Honda started using this term around 1998 or so when they combined the ECM & TCM into the same case.
 

ok so the PCM is the ECU/ECM and all that... ok that answers many questions... so real quick one more question... where is the PCM located in my 1999 honda accord.

If it's the same thing that I hooked my VAFC up to, its underneath the center console behidnd and below the radio ..... kinda near the passanger's left foot.  I thought that was called the ECM.   I also thought that the TCM is the blue box by the passanger's right foot, but I could be wrong.

Forward & below the center console.  The wiring harness comes in from the right side, so look in the passenger footwell.  You may need to remove the side panel from the console, but what you really want to do is peel down the carpeting alongside the passenger's left foot.
 
Falk, that box over in the right kickpanel may have been where the tranny controller was before they started combining them together.  Or maybe it's the ABS??
 

Just curious....who tested it for you?
I don't know if I have ever heard of an ECM, PCM, ECU, etc.. cause a P1457 code.  I think someone may have given you some false information

A faulty PCM is way down on the list for P1457, but it IS in there.  After you have ruled out about 2 dozen other things.  The procedure in the Helm book is probably 12 pages of things to check.
 
But a faulty PCM seems to be included as a last resort in almost EVERY OBD-2 error code...
 
My personal opinion is you wanna spend time checking & ruling out EVERYTHING ELSE first.  Automotive computers are surprisingly robust.  And it's real easy for a shop to sell you a new computer for a few hundred $$ while at the same time fixing the broken wire that they found after 4 hours of electrical tests.
 

well i pulled the code my self... then took it to carmax only because i work there and i get a discount on service. the mechanics performed all the tests and basically everything came back ok except the feul tank pressure sensor which they cant test. or the PCM is faulty.. its one of the two... so the way i look at it is can buy a PCM off of a 99 accord that has been pulled out and just replace mine because they go for about 50 bucks used but i have found many that will give me a warrenty on it. or i can pay 100$ for the sensor not mention the labor and that might or might not do it. so im gonna do the cheap one first and if its not a fix then ill get the sensor. 

question about PCM/ECMs... is there a differance in the unit in a normal 4 cyl accord compared to a vtec 4cyl accord... in other words will any PCM out of a 99 accord lx work in my 99 accord lx 

I'd guess they're different so you have to get one from the right engine.  There's 3 different 4-cylinder engines.
F23A1
F23A4
F23A5
 
I think the non-VTEC engine was only on the DX, but I'm not too certain about that.  The other one is ULEV (California) engine.
 

alright.. well i found a ecu with exact matching #'s so its ok... thanks for all the help guys

ok so i got a PCM its used out of a 99 accord... and the modle # is the same as mine.. i plug it in and my car wont turn over... it sounds like it wants to but it wont.. now besides that it may just be a bad PCM is there anything i have to do to get a different PCM to work or is it just supose to be plug and play?

If you mean it cranks but won't start, it's probably the mmobilizer...
Did you get a key from the donor car where the PCM came from?
 
There's an RFID chip inside the key.  There's a small antenna near the ignition switch.  If the key isn't on the list of 'authorized' keys in the PCM, it won't start.
 
Take the key from the donor car (it won't work in the actual lock cylinder).  Hold it up against the steering column & try again.
 
Once you know that's the reason, you'll have to go to a dealer or locksmith who has the computer to program your new ECU to accept YOUR keys.
 

makes sense.. ill see if i can get the key but i doubt ill be able to do that.. but lets hope for the best. thanks alot.. again!!

I would be willing to bet money that you need one that matches your engine code.
Here are the differences:
F23A1 - LEV VTEC - it will simply say "VTEC" on the valve cover
F23A4 - ULEV VETC - it will say "ULEV VTEC" on the valve cover
F23A5 - non-VTEC - only found in the 98-02 Honda Accord DX models - will not say VTEC on the valve cover

Your engine code can be easily seen stamped on the engine to the right of the exhaust manifold.
 
Woops - I forgot to check page 2.  Looks like you already got the PCM

ok well before i go and and try and find the key and such.. i need ur opinion... so since the only two things that the mechanics say it could be is the fuel sensor or the the PCM... when i clear the code in my car.. and drive it for a few hundred miles... and scan it.. my scanner says that all systems yhave ran their test and passed and i get a green light.. but then i drive a bit more and then the P1457 evap code pops up... thats why i think its the PCM cause everything passes and then a bit later the code pops up.. so what do you guys think... or does none of that matter?

I think the EVAP codes can be delayed, like this...
 
The system only OCCASIONALLY tests itself to see whether the tank & canister are airtight.  It has to fail those occasional tests a couple of times before it throws the CEL.
 
Can your scanner display 'readyness' codes?  Basically, if you reset the ECU it may take several days of driving before ALL the systems test themselves & set the readyness codes.  This clever bunch of nonsense is designed to prevent people from clearing the error codes in the parking lot outside the emmissions testing station.
 

no i my scanner cant read those... well i i think ill return the PCM for now.. and just replace the Fuel sensor first... and ill see what happens if it turns on then ill get the PCM and have the keys reprogramed

You said the shop tested all the stuff...  One item is the canister itself.  Is it possible they tested all the valves but didn't check the canister itself to be airtight?
 
There's a bunch of vacuum hoses down there around the canister, & going up front to the EVAP purge valve (on the intake manifold).  Maybe a vacuum hose is either disconnected or cracked?
 

Dunno if you have already sorted this out or not, but my car had the same code. Some bimbo at Advanced told me it was probably the O2 sensors and without any more research I went for it. After finding out the hard way that didnt work I took her to Honda for a smoke check. Turned out to be two sensors in the evap control system, not sure the parts numbers, and I managed to get out of there without paying for the test. I will look up as much as I can from Honda to find out what they said, as it's been a while since I had it tested.
Ty