Ongoing evap CEL

[Nolfol]

we still cant find what is wrong with this thing it will pass test 5 times then fail . so far we replaced purge valve, close canister valve , all tank gaskets, fuel pressure sensor . im leaning towards a ecu now but damn thing is on backorder with no release date .

had to hold off on fixing her
So Still waiting to do the ecu on mine
Cause wife lost her job with the pandemic B/S
So had to hold off $ wise
so haven’t been driving it much I just use her car.
The genny sat in the garage all of the winter.
So gonna take the new stimulus $ and have it put it in hopefully it fixes it

 

[MG8]

had to hold off on fixing her
So Still waiting to do the ecu on mine
Cause wife lost her job with the pandemic B/S
So had to hold off $ wise
so haven’t been driving it much I just use her car.
The genny sat in the garage all of the winter.
So gonna take the new stimulus $ and have it put it in hopefully it fixes it

i wish you the best of luck, as for me im growing frustrated. car runs perfectly fine just wont pass smog.

 

[Husky]

How about a corroded connector somewhere, with all these sensors, etc...? Just throwing that out there. To me it seems unlikely to be the computer, but rather something simple, especially given the mileage.

 

[MG8]

How about a corroded connector somewhere, with all these sensors, etc...? Just throwing that out there. To me it seems unlikely to be the computer, but rather something simple, especially given the mileage.

This thing will pass the the test like 3 or 4 times then fail that makes me believe that there is no leak because a leak would be consistent and fail every time. So what your saying may be a option.

 

[Husky]

Intermittent problems like that also sound more like a bad connection somewhere than a bad computer.

 

[Husky]

Does this cause a CEL or something that you can observe while driving? (Sorry if you already mentioned this ) If so, look for patterns and correlation. Does the error show up when driving on a bumpy road, or when it's wet, for example?

 

[MG8]

Does this cause a CEL or something that you can observe while driving? (Sorry if you already mentioned this ) If so, look for patterns and correlation. Does the error show up when driving on a bumpy road, or when it's wet, for example?

Car runs flawless just stupid cel.

 

[MG8]

It will complete a drive cycle then come back on when it wants to.

 

[Nolfol]

Ya I hear on the frustrated part
And my car runs fine as well.
I clear the cell and it’s random it can pop in 180 miles or 20 miles .
Every evap part replaced ,smoke tested so many times starting to lose count lol
If the ecu doesn’t fix it dealer won’t charge me for the part they said minus labor

thought about throwing a used one on myself
And seeing if it works
Dealer won’t use a used one
I dont have to do emissions till
November so have a little time to figure it out

 

[mikec]

For those with sporadic evap CEL codes, besides the stuff I posted on the first page of this thread, some other things to examine and some tests you can try:
An insidious source of leaks is the fuel filler nozzle itself - where the gas cap gasket seals. If the filler nozzle surface has scratches, dent, or crud build-up, the gas cap gasket won't be able to do its job. I had something like that on my Corolla a while back - it's a carbureted engine so no OBD-II codes... but, during a SoCal smog test, it "failed" the shop's evap system test. Basically, on non-OBD-II cars, the shop hooks up an air hose in place of the gas cap, pumps air in or out of the fuel tank to a pre-determined pressure level, then monitors the pressure for a while to see if it significantly changes (=fail) or holds fairly constant (=pass). My Corolla "failed" because the filler lip was dinged so the smog test tool couldn't seal properly. Doubling-up the test rig's gasket made my car easily pass. I've since re-done that surface so subsequent smog checks haven't had issues. Check your car's filler neck.

Other posts ask when the CEL appears - is there any pattern? Rough roads, hot days, cold days, long drives, short drives, etc. Another test to try: next time you fill up, fill the tank completely and then reset the CEL. Watch the fuel tank level; when the tank gets to half-full go ahead and re-fill it. Repeat that cycle if the CEL stays off. If the CEL appears, drive until the tank is nearly empty... then refill to only half a tank and reset the CEL. Basically, see if you can correlate the CEL triggering based on fuel tank level. The more fuel in the tank the less air space there is... so air leaks can affect the pressure/vacuum in the tank more quickly. That's why the computer may think "massive leak" if the pressure changes rapidly because the tank is full so a puny air leaks drastically alters the vacuum. You may find that driving with no more than half a tank of gas keeps the CEL off... a way to at least get past your next smog test until the real problem can be found.

mike c.

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[MG8]

Ya I hear on the frustrated part
And my car runs fine as well.
I clear the cell and it’s random it can pop in 180 miles or 20 miles .
Every evap part replaced ,smoke tested so many times starting to lose count lol
If the ecu doesn’t fix it dealer won’t charge me for the part they said minus labor

thought about throwing a used one on myself
And seeing if it works
Dealer won’t use a used one
I dont have to do emissions till
November so have a little time to figure it out

i cleaned some connectors clear code, drove 249 mile than came back on with same po456 smh idk what to do at this point.

 

[MG8]

Ok so I literally ran into a wall , I went and replaced the ecu with a brand new ecu. The cel same P0456 is still on, im lost for words I don't know where to go from here.

 

[MG8]

On the good note this cel is so inconsistent I was able to set the monitors and get it to pass smog. That will get me by till next April.

 

[Nolfol]

Ok so I literally ran into a wall , I went and replaced the ecu with a brand new ecu. The cel same P0456 is still on, im lost for words I don't know where to go from here.

Well that’s good news and bad news
So now I don’t have much faith in the Hyundai engineers that suggested to change mine when the dealer called them for help diagnose the car
After repeated attempts to figure this out

 

[Husky]

That sucks. Intermittent failures are such a bitch to troubleshoot. My money is still on a flakey connection somewhere. I realize that doesn't help much.

 

[mikec]

When dealers try to diagnose OBD-II error codes, one thing they are supposed to do is review the Technical Service Bulletin (TSB) history. There have been several software updates for early model year Genesis sedan engine computers... some of which specifically target P0456 slow Evap System leak. Replacement ECMs come with the ORIGINAL software installed - not the latest and greatest. So, when ECMs get replaced, the dealers have to apply all applicable TSB updates. My dealer didn't do this after my ECM change. (It was really dying, caused my V8 to run horribly at times, stall coming to a stop sign/red traffic light until the engine warmed up a bit) So, after getting a new (and expensive) ECM, P0456 kept popping up.

P0456 applicable TSBs for 2009/2010 Genesis sedans include:
09-FL-009
10-01-025
10-FL-015 (this one also addresses potential "random/multiple misfires" OBD-II codes)
13-FL-009

Some of these were done as service campaigns too; when you bring your car in for any service and the service adviser enters your VIN, the Hyundai service tracking system computer should note that your car is missing this campaign and it should be performed for free during this visit. You can always ask the service adviser to check for missing campaigns and to verify your ECM is in fact at the most current level. They should do that for free; it only takes a couple minutes using the standard Hyundai tech's GDS and VCI tools.

mike c.

 

[Pappy ElDuderino]

Isoltated the system in sections. Filler neck to tank smoke tested, went to 0. Purge valve went to 0. Hose from purge valve to canister with evap hose to gas tank removed and blocked port, went to 0. Tank disconnected, smoked through filler neck port and evap hose to cansister removed and blocked, didnt go to 0. Can not see where evap hose goes to tank, but can see the two lids for pump and sender not smoking. going to assume the two evap connections from canister evap hose to tank is the problem.

 

[Early gen 1]

It’s started out months ago as incorrect purge flow .
so replaced both solenoids ,gas cap,pvc valve (do to mileage) So that corrected it until week later ... small leak popped up
Re checked fitting etc ,
Decided to bring it the dealer for smoke test found no leak ,they thought it was bad rear solenoid I just put in ...they ordered another .
Another trip there oops It’s not the soleniod now they found a leak in filler tube they took a video of it during smoke test .
so they order new one And replace it re test it all good no leaks
Cell still on for gross leak
They call corporate tech support .they say to weigh the canister if it’s over 3.5 pounds replace it
Mine weighs 3.0 ...
If not that it needs new pcm
So now I’m into this evap issue for $730(my parts and there parts +labor)
and now they want $1200 for new pcm without labor
Any body have similar issues ? I searched but couldn’t find similar

Similar issue. Had to clear the code manually, driving didn't do it. Clearing the code wasn't easy. Wouldn't clear while car was on or off - it needs to be in between (full ignition on, engine off). No, Acc won't cut it. Full ignition, engine off.

Once I cleared it, filled up the tank and ran it 25 miles, passed emissions and registered!

 

[optimagenesis]

Similar issue. Had to clear the code manually, driving didn't do it. Clearing the code wasn't easy. Wouldn't clear while car was on or off - it needs to be in between (full ignition on, engine off). No, Acc won't cut it. Full ignition, engine off.

Once I cleared it, filled up the tank and ran it 25 miles, passed emissions and registered!