I've had the Service Light on for quite some time now with the subject codes. After a long research, I did nothing to fix it since the problems could be so many with the EVAP system. There are two possible valves, the canister, the gas cap, and all the respective hoses that could be at fault.

Coincidentally I get the exact same code on our Nissan Armada. That one though pointed to the purge valve only. While I was at the parts shop I asked the guy why I had gotten the codes on both cars. He, by chance, had the same code on a Pontiac a while back.

The reason - topping off your gas tank.

In the old days it was customary to do so and not a problem. With today's emission systems when you top off you actually send pressure and fluids into the vent lines, which cause the malfunction.

On both cars I stopped topping off and by the second tank refill, the light had turned off.



So, if you get the code(s) and you top off, before you spend any money, wait a couple of tanks, you might get lucky.....

 

^^^ good tip!

When the pump clicks off, STOP. If you don't there is a good chance you are filling the charcoal canister with gas and it will set a code.

In the "old days" the tank was vented to the air and it wasn't a problem. (good for the car, sucks for the environment)

 

So, the canister does not come up as a faulty part, only the purge valve. What do you do? Change them both?

 

You must have really been trying to squeeze every last drop in there. I usually go two clicks (on some pumps the automatic shutoff misfires before your tank is full) and have never had an issue. I've even had some pumps fail to shut off and dump gasoline down the side of my car and, of course, the professional gas pumpers in New Jersey are experts at trying to get every last ounce into your evap canister. Regardless, still no faults.

 

Tick - tick - tick.... it is only a matter of time.
With your inexpensive gas prices, why do this?

 

Criledo:

Here are Nissan/Infiniti's definition of the codes:
P0455: EVAP control system gross leak detected
P0456: Evaporative emission control system very small leak (negative pressure check)

These codes have nothing to do with over filling the tank. You have an EVAP leak or two.
EVAP codes are not hard to fix, but do require methodical testing of EVERY hose/pipe/solenoids in the evap system and there are quite a few.

From my experience I would look at/test the canister vent valve first then the EVAP canister purge control solenoid.

 

As an aside, when I was filling up last week my needle got stuck at 75%. Before I told the guy to top off my tank, I fixed the problem by turning the battery off and on again. I guess there's fail safes in place for a reason?

 

4 cars with evap over 15yrs, never an issue. I only ever hear about this with people who are OCD about getting an even dollar figure

 

Couldn't a bad gas cap seal do the same?

 

Actually it's the first recommendation everywhere I looked. Check the cap first and many people have reported thew problem to have resolved that way.

 

It could be the gas cap....
Most places say to replace the gas cap as it is cheap and easy first fix. However, they are also very simple devices, durable and usually aren't the EVAP leak, unless they were not properly tightened.

The only way to know for sure, it to buy an Infinity gas cap and see.

I would still test the canister vent valve. This valve is open all the time EXCEPT when testing the integrity of the EVAP system. Since it is open so much, water can enter it and cause a little corrosion, which results in a small/large leak.

 

SonicVQ, thank you for your post.

When this first came up, we read the code at a Auto Zone and got the gas cap from the Infiniti dealership. No change.

The light started to go off at times but always kept coming back. With time 0455 was joined by 0456.

I researched a lot and the one conclusion I draw is that there are many things that could be at fault, but the first recommended part is the purge valve. The report does say that it could also be the vent valve, or worst case the canister itself.

I got the purge valve as recommended first. I will take the time to test the vent valve make sure it is working properly and also inspect the canister while I'm at it.

A lot of people say it's a pretty crappy situation as a lot of parts could be faulty and it's a waste of money to just throw parts at it and see which one it actually was.

Thanks for your post and the instructions to test the vent valve, it's definitely a good help and will be done.

Guess what I'm going to be doing on the weekend.....

Thanks again,

Chris

 

Not OCD, just trying to totally fill up and extended the need to stop next time. I've learned my lesson, when it clicks, it's done........

I traveled to South America recently. My jaw dropped when I saw taxi cabs driving the rear left tire on a wooden block they keep in the trunk, to make it higher so even a bit more fuel will go in. Oh boy are they in for a nasty surprise.......

 

Got the light off today, YAAAY!!! Happy New Year!!!

Changed the tank cap, then the purge valve (underneath hood compartment) and the light went OFF after a couple days, for a couple days and came back ON again. Then I changed the vent valve (underneath car behind the right rear tire) and it has now turned OFF. After 4 to 5 miles..... Problem Solved!

 

That is great news! Thanks for the update.

What made you change the purge valve?
What year is you car?