EVAP system CEL P0456

I've been getting the P0456 code on my 08 Tacoma.

This is very useful;

My question is during "Operation C: EVAP pressure Measurement" the pump discharges into the cannister filter. The filter is connected to the tank filler neck below the gas cap so it's connected back to the tank. So how can it draw a vacuum when it's pumping in a loop?

Thanks.

 

Surprised that no one could answer my question. Fortunately I was able to make a fix that has cleared the code. Put hose clamps on cannister filter hoses.

 

I believe that, normally, the EVAP system carries a vacuum.

But when the vehicle is first started, a small pump pressurizes the system and checks for a leak (holds the pressure). If a sensor detects a leak-down, it throws the code. If it can't hold a small pressure, then it can't hold the vacuum either.

At least this is how our 2002 Dodge does it. I had to replace a split vacuum hose when it threw an EVAP code.

 

I had a careful look at the filler today and, sure enough, just under the lip on the right side of the filler there's an opening for the vent line. So the vent system does vent to atmosphere.

Tan4x4 if you read the link in my first post it explains how the system works and not how you have described.

 

I got this code as well. My own mechanic skills and tools are rather limited. What is it that you did to fix it? I also have a family member with expert skill when it come to this sort of thing. So whatever you can tell me I can pass along and he can help me do it. Thanks!

 

In the end I replaced the charcoal cannister assembly and the code has gone away. When I took the old one apart it appeared that the very tiny vacuum pump was ceased. Reread my other comments and look at the link to understand how the system works. Basically it wakes up in the middle of the night and draws a vacuum to see there are no leaks.

 

Been getting this code on and off for awhile, now it finally seems that its here to stay. Before I take it to get checked out (hopefully under my extended warranty) I want to try this hose clamp fix. Where are these cannister filter hoses you speak of? Pics? Thanks!

 

While doing a search I came across some old posts by me when I was hunting the P0456 problem. I want to update it so if anyone else is looking they get the right answer. What it did turn out to be was that the diaphragm in the refuelling valve was ruptured. It is a used truck so maybe overfilling the tank by the PO or an accident caused the rupture. Unfortunately the solution was the very expensive charcoal cannister assembly.

 

I just got the P0456 code. I cleared it and opened and closed my gas cap. I’ll post back what happens next.

 

So far so good. I had just gotten gas the day before the light came on. Hopefully the cap was loose or maybe it was over filled.

I’ll post back it if happens again.

 

Any updates on this?

 

I seem to get this code on particularly cold days (by comparison) in the south. I typically only get the "Pending Error Code" message on my Ultragauge. Only once has it turned into a full blown CEL.

 

Hi! I just got this code.

I started my truck having an almost empty gas tank. I was planning on refueling today because I came home late yesterday.

would it be that? That I am almost on empty tank?

Any help is greatly appreciated

 

A little vacuum pump in the charcoal canister assembly tries to draw a vacuum on the fuel tank to make sure there are no leaks. If the gas cap isn't closed or if the tank is nearly empty (lots of air to pump out) or the pump is getting old then you can get this error. Fill your tank and reset the code and see what happens.

 

Making sure the gas cap is tight is where I'd start

 

Hi man! Thank you very much.. this is the first time it happens to me and I have a keyed gas cap that I've been using for about 4 years now.. I had the low fuel warning this morning.. I went to gas station, filled and inspected gas cap and it looked ok.. tightened gas cap until it clicked (like I always do) and gone...

Thanks for the help!

 

Problem solved! Thanks!!!

 

This could be your problem. Keyed gas caps aren't (typically) air tight like non-keyed versions.