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2003 with a PO456 Engine Light Code

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Old 08-08-2012, 11:21 AM   #1
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2003 with a PO456 Engine Light Code

Not a Day after new front Struts and the engine light comes on. I'm at 120,000 and have had the light come on before for the front exhaust sensor.

PO456, Autozone's Reader said it could be: Faulty Fuel Cap, EVAP Line Linkage, Pump Module Failure, or Canister Faulty.

Indeed I do occasionally smell gas (recent). Anybody deal with this on there own, and how did you get the light to go out (besides unhitching the battery, pulling a fuse, lol)

Hate to go to the Dealer $$$.

-Ugmold
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Old 08-08-2012, 11:27 AM   #2
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Pull the efi fuse to reset the light and see if it comes back on. Could be a fluke deal.

Then start with a new fuel cap. They are like $7 and it will rule that out immediately. Pull the efi fuse after you replace it and see if it comes back on.
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Old 08-08-2012, 11:30 AM   #3
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Fix the leak.

If the fuel cap is on tight (loose cap is the easiest way to pull one of these and also the easiest to fix), look to see if the gasket is suspect. If so, new fuel cap. Also look for loose or cracked hoses in the evap circuit (you smell gas, I'd bet there is one), repair or replace as needed. Light will (eventually) go out all by itself if you fix the issue, for this particular one. If you don't fix it, any way you turn the light off, it will come on again (and you'll be evapoarating gas you could be using in your engine, which is kinda silly at today's gas prices...)
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Old 08-08-2012, 11:52 AM   #4
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Is the Cap supposed to NOT vent?

What is the EVAP Circuit? I looked at the hoses around the engine and briefly looked around the gas tank, didn't see anything apparent, but obviously could be.

What is the cannister?

The smell of gas I think makes it obvious I do have some kind of problem.

I'll take a look at the cap when I get out of work.

Thanks a lot!

-Ugmold
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Old 08-08-2012, 09:01 PM   #5
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IIRC, The cap only vents after a certain amount of vacuum or pressure is applied - if the sensor does not see that happening, it throws a code. When I've drive a bit and stop, I can hear the cap vent working for a little while after I shut down.

There's a link to the factory service manual in one of the stickies which will have the whole system explained. Basically, rather than a simple vent, the venting is mostly run through a charcoal canister (in the engine compartment, I think) that is supposed to trap most of the gasoline vapors - then when you start up the truck, that canister is "purged" into the intake so the trapped gas vapors run through the engine and get burned (and the canister is ready to trap more at the next stop.)

So - loose cap will throw the code. Cap with bad gasket will throw the code. Leaky or disconnected hose will throw the code. Bad sensor will throw the code. Smell of gas is a good sign that it's probably not a bad sensor.
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Old 08-08-2012, 09:01 PM   #6
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P0456 is the code for "small leak detected" This means that a leak that is considered less than .010" in diameter has been detected.

The EVAP system is designed to prevent the SMALL amount of gas vapors that evaporate from your fuel from exiting the system into the atmosphere. Today's fuel caps are supposed to completely seal the filler neck from any type of leak. I would think that since you just had new front struts put on that someone accidentally knocked a hose loose. Follow the hoses from the EVAP canister which is typically located under the hood, on the driver's side fender. It will be a black box about 8 inches long, 4 inches wide, and 4 inches tall (this is general, but not exact) Look at all the hoses that come from it and follow them to make sure none have come loose, or possibly cracked. I would think a small leak would likely come from a crack in a hose rather than one that were totally disconnected. Only reason I suggest this particular check is because you mentioned it happened the day after the struts were replaced.

Barring that, A quick check of the gas cap to make sure you tightened it the last time you put fuel in would be a good idea. Rule of thumb is tighten cap until you hear a MINIMUM of 5 clicks.
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Old 08-08-2012, 09:09 PM   #7
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If you replace your cap in an effort to chase down an issue, replace with toyota cap. Some cars cannot use aftermarket caps and will throw a code. Spend the extra couple bucks and go OEM. Know anyone with a smoke machine? Good for looking at leaks in evap system.
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Old 08-09-2012, 01:27 PM   #8
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Watched this video of the evap system (new to me) on youtube. I get an idea of how it works anyway.

http://www.youtube.com/watch?v=Dfj-F_pTj5M

Tonight I'm going to check the hoses, I looked at the cap, looks healthy, but I think the last couple of times I got gas I didn't click the cap after filling, just tightened it w/o click. I could smell gas this morning.

Not fun checking gas tank hoses with all that black "rust proof" crap Toyota sprayed on after the re-call, it is falling off anyway.

I really appreciate the help thus far and will report back.

-Ugmold
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Old 08-10-2012, 07:04 AM   #9
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Quote:
Originally Posted by ugmold View Post
Watched this video of the evap system (new to me) on youtube. I get an idea of how it works anyway.

http://www.youtube.com/watch?v=Dfj-F_pTj5M

Tonight I'm going to check the hoses, I looked at the cap, looks healthy, but I think the last couple of times I got gas I didn't click the cap after filling, just tightened it w/o click. I could smell gas this morning.

Not fun checking gas tank hoses with all that black "rust proof" crap Toyota sprayed on after the re-call, it is falling off anyway.

I really appreciate the help thus far and will report back.

-Ugmold
Good basic video. And if you tightened your cap but didn't make it click, that would be the most likely answer right there.
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Old 08-10-2012, 07:41 AM   #10
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Going to put a guess in that it is a V6? If so here are some FSM pages on the emission system that may help you cure the issue. Probably way more info than you need, but hope it helps. Hope it is a simple repair for you.

Was not on a Tacoma, but a family member had a check engine light come on and called the dealer about it. First thing they said was to check the fuel cap was tight. Also with BamaToy that would pay to double check all the systems up around where you had work recently done. Would not have thought that they should have damaged anything, but you never know.

http://www.ncttora.com/fsm/2003/Repa...eecsy/comp.pdf
http://www.ncttora.com/fsm/2003/Repa...eecsy/insp.pdf
http://www.ncttora.com/fsm/2003/Repa...plasd/draw.pdf
http://www.ncttora.com/fsm/2003/Repa...plasd/loca.pdf
http://www.ncttora.com/fsm/2003/Repa...vfccv/insp.pdf
http://www.ncttora.com/fsm/2003/Repa.../vfee/comp.pdf
http://www.ncttora.com/fsm/2003/Repa.../vfee/insp.pdf
http://www.ncttora.com/fsm/2003/Repa...vfpsv/comp.pdf
http://www.ncttora.com/fsm/2003/Repa...vfpsv/insp.pdf
http://www.ncttora.com/fsm/2003/Repa...e/vps/insp.pdf
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Old 08-11-2012, 01:25 PM   #11
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I'd go work on it if I could stop watching BamaToys animated gif. lol.

Thanks for all those links. It is actually a 4cyl. 2.4L.

I gave everything a look over, the only hose that looked cracked was the small one that runs to the air filter. I cut a 1/4 inch off and thru a mini clamp on it.

I guess I was hoping for the light to go out. I'm going to pull the fuse and see what happens, hoping the cap or the connection at the air filter solves it.

I'll post back and thanks.

-Ugmold
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Old 08-13-2012, 07:27 AM   #13
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Well just under 100 Miles and the light has stayed off after re-setting the EFI Fuse. No Gas smell. Fingers crossed.
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Old 08-13-2012, 07:41 AM   #14
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Quote:
Originally Posted by ugmold View Post
Well just under 100 Miles and the light has stayed off after re-setting the EFI Fuse. No Gas smell. Fingers crossed.
The P0456 code is a finicky one when it comes to testing. You have to perform multiple drive cycles. Of course I am hopeing for the best here, and like I said, that gas cap thing is VERY common and I suspect since you mentioned I believe that you never "clicked" it, that your problem was there. Good luck and I'll keep my fingers crossed for you!
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Old 08-14-2012, 07:25 AM   #15
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Thanks Bama and Hillingdoner.

No light still this a.m. but I did fill up with gas right around the corner from work. I figure a full tank could be a factor as well.

I'll keep you posted.

-Ug
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Old 08-22-2012, 08:23 AM   #16
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After 1 + fill-ups the check engine light remains off. However I do still smell gas and cannot track it down. I'm betting it is the cannister ($).
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Old 08-22-2012, 10:28 AM   #17
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I'd still bet on hoses (cents or not too many $). Or valve ($).

Unless you manage to crack the thing, there's not much to go wrong with the canister. It's a box with some charcoal in it. Fuel vapors go into it while you are parked, and fresh air is pulled through it into the intake when you are running, so it's got room for more fuel vapors the next time you stop (and the stored vapors get burned, rather than venting to atmosphere unburned.)
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Old 08-23-2012, 09:14 AM   #18
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I only smell gas when I open the door, I sniff around and nothing. Or in commuter bumper to bumper traffic, wafting in the rear window.

-Ugmold
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Old 08-28-2012, 05:16 PM   #19
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I'm getting a PO442 and a PO456. Aren't those telling me the same thing or is the 456 a leak and 442 a blockage?
Anyway I checked the codes expecting an O2 sensor code since I'm getting intermittent slow accelerator response, particularly when it's warm out like over 80 degrees.???
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Old 09-04-2012, 01:51 PM   #20
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Light is back on, smell the gas, I think I'm bring to Ernie Boch Jr, the dealer.
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