P0456 Code

Knightryda · Post by **Knightryda** » Sat Jan 05, 2013 5:55 pm

Okay so the code is very vague. I guess my question is, Could this also be vacuum leak? And what is the probability of the problem being a faulty gas cap?

Soundwav · Post by **Soundwav** » Tue Jan 08, 2013 2:09 pm

I had this code few weeks back
i replaced the gas cap and it still was kicking around
bough a new muffler, threw that on and have not had the code since....

been two weeks of running the car 4x a day to see if it comes back
as it needs to go for etest..

so far so good no issues yet!

Not saying go out and replace your muffler
but thats what i think cleared it up for me!

RobsProjectSOHC · Post by **RobsProjectSOHC** » Tue Jan 08, 2013 3:50 pm

I have this code with a couple of others. You could look at your vacuum lines for cracks, but i read its mostly gas cap, o2 sensor, exhaust.

Well, tomorrow im replaying the 02 (downstream) with an all new SS exhaust, headers to the muffler.
if it doesnt fix then idk

stdlystdmufn · Post by **stdlystdmufn** » Tue Jan 08, 2013 6:16 pm

it only applies to the EVAP system. so doing anything with the exhaust is not going to directly fix the issue.

Post by **occasional demons** » Tue Jan 08, 2013 10:06 pm

Basically it is a small leak detected. You have to check every tube/hose on the evap system, including the filler neck, and anything attached to the fuel tank. Most times it is the hoses at the nlvd or the charcoal canister.

It can be either an easy fix, or a small nightmare tracking it down.

Replacing the muffler, might have bumped something near the charcoal canister/pump, and temporarily sealed the leak.

viewtopic.php?t=28793

gcretro · Post by **gcretro** » Fri Sep 27, 2013 11:37 pm

on my 04 neon se, this p0456 shows up if I drive hard. Last week I red lined the motor touching 6 to 7K rpm couple of times... Next day morning, greeted with P0456.

I suppose at higher revs, there is more vacuum? causing a greater chance of a leak?

Post by **occasional demons** » Sat Sep 28, 2013 12:17 am

Actually running it that hard, the manifold vacuum is probably much lower.

The LDP basically pulls a vacuum on the system. How well that vacuum holds is what it is monitoring. The way you drive likely has nothing to do with it. Other than how inertia is pulling on the various hoses and other components...

C1DoG · Post by **C1DoG** » Sat Sep 28, 2013 7:55 am

OD... Does it affect fuel mileage at all? I have been running the code for over a year now, and I am just curious if it does.

Post by **occasional demons** » Sat Sep 28, 2013 11:19 am

I don't see why it would. It has nothing to do with engine management.

It is more of an environmental protection thing. They don't want un burned hydrocarbons escaping into the air. The vacuum is how it monitors that the fuel tank is sealed.

Give them time, they'll have o-rings in the filler neck to seal the fuel nozzle while you fill up.

C1DoG · Post by **C1DoG** » Sat Sep 28, 2013 3:00 pm

Alright cool... Like I said I was just curious.

gcretro · Post by **gcretro** » Thu Oct 03, 2013 10:58 pm

gcretro wrote:on my 04 neon se, this p0456 shows up if I drive hard. Last week I red lined the motor touching 6 to 7K rpm couple of times... Next day morning, greeted with P0456.

I suppose at higher revs, there is more vacuum? causing a greater chance of a leak?

Well I was driving with quarter tank of gas or lower. Filled up and the code/light went away...

SleepySRT4 · Post by **SleepySRT4** » Wed Oct 16, 2013 6:22 pm

I have this code currently. I pocked my head under the car and noticed that the uncovered side of my evap canister was gone!

I plan on replacing it but haven't gotten around to it yet.