P0455 - Need Help Troubleshooting
 

I've done some digging on this code and know that it effects the EVAP system and is a large leak. I also know that it could be any number of things causing the code.

I have checked but not replaced the gas cap and it seems to be fine. I may replace it for good measure, but I doubt it is causing the issue.

I'm not sure if this is related or not but I have been getting poor fuel economy lately (around 14mpg as compared to the normal 17-18mpg) and also notice a faint gas smell on occasion from what seems like the driver's side (it's quite difficult to pinpoint). I have not seen any gas puddles on the ground.

The car drives good, no starting issues, smooth idle and acceleration, no smoke.

I am thinking of checking the EVAP purge and vent solenoids, but beyond that I have no idea what to do. I'm also not entirely sure where those solenoids are located or how to test them. I believe I need some way to provide power to the solenoids to test them properly.

Any help is appreciated, I have been idly dealing with this issue for a few months and am getting very frustrated by it. Thanks.

Couldn't get to test the solenlids today, got rained out. Now I won't be able to check the solenoids until this weekend.

P0455 is in fact a large leak, (.030" or greater) in the EVAP system or, no purge flow when commanded. It will not affect driveability, but it can cause a raw fuel odor from wherever the leak is. The most common cause is a faulty seal between the gas cap and the filler neck. The purge solenoid is located on the passenger side of the intake plenum, just rearward of the ignition coil. On a 2 door, the vent solenoid is behind a plastic shield mounted to the frame crossmember just forward of the fuel tank. On a 4 door, IIRC.... uh nope, can't remember at all ;) Maybe someone will chime in. The purge solenoid is controlled by the PCM using a duty cycle. The vent solenoid is also controlled by the PCM, it's either on or off. EVAP leaks can be very frustrating to locate as they can be almost anywhere: fuel tank, filler neck, purge canister, fuel cap, vent line, or any of the associated lines between the fuel tank, purge solenoid, vent solenoid, and purge canister. An inches of water, (not mercury) vacuum gauge, and a hand held vacuum pump come in real handy when looking for EVAP leaks.

HamToast, I looked at your old posts and missed what you are driving, what are you driving?

Don't know why I didn't include it! It's a 2005 2dr S10 Blazer 4x4.

ever figure out what is was? im getting same code 04 blazer 4 door i replaced fuel cap no help

04SSBlazer, Read post #3, it gives the possibilities. Here is a link to the flow chart, follow each step exactly as outlined and it will take you to the problem: https://blazerforum.com/forum/diagno...0-370-a-53332/

Any tips on finding leaks in the EVAP system? Changed the fuel pump last weekend in my 03 Blazer 2 door, now I'm getting a P0455 code. Unless it's a major coincidence, I must have messed something up. Could be the EVAP hose that connects directly to the fuel tank, or the filler neck/hose. Those are the parts that I had to connect/reconnect while doing the job. The diagnostic flow chart for P0455 requires you to have a smoke machine in order to properly use the chart, obviously I don't have one. I'd rather not use trial and error when determining the leak, especially since I will have to drop the tank again if it's the hose that connects to the tank. I want to be absolutely certain that I am repairing the right part, not just guessing.

Oh yeah, the gas cap isn't loose, that was the first thing I checked.

P0455 is a "large leak" in the EVAP system. Obviously, to be absolutely certain that you're repairing the right part, and not just guessing, you need to follow the flow chart, smoke machine and all ;) Could be any of the things you mentioned, and then some. Fuel filler neck and vapor line connection on the tank would be the first things to check.

Just got a new filler neck in the mail today, hopefully replacing the old rusty one (along with the rubber hose) will solve this leak.

One question, will this condition cause fuel mileage to drop? Pretty much since I've owned this vehicle, it has consistently gotten 18-19 MPG. I check at almost every fill up. However, the last two tanks of gas have only gotten 16 MPG. And it was two tanks ago that I replaced the fuel pump (and theoretically caused this leak), so I'm wondering if this P0455 code has anything to do with that. I've cleared the code twice during this time, not sure if that would have anything to do with the drop in MPG. Right now I just left the SES light on, I'll clear it again tomorrow after switching out that filler neck to see if that fixes it.

I haven't changed driving styles or driven the truck anywhere differently than normal. Plugs, cap, rotor (Delco) are all new, also new Autolite wires. Tires are at the proper pressure. Not hauling any extra weight, so just wondering if this code has anything to do with it.

Another place for a possible EVAP leak is at the fuel pump module O ring. Did you lube it before installing the module? Did it seat completely without getting distorted when tightening the retaining ring?

Very few EVAP codes will cause any noticeable difference in performance or fuel mileage. Especially not the P0455, unless fuel is leaking out ;)

If the distributor has been out, and camshaft retard is not within specs, that could cause a slight drop. With colder weather approaching, it's possible the drop is normal as the PCM keeps the fuel mixture rich longer during warm up... colder ambient temp equals longer warm up time. Might want to jack up all 4 wheels and make sure that no brakes are dragging.

EDIT: make sure the fuel fill cap gasket is good, no cracks etc.

Thanks for the helpful tips Captain. The cold weather may be the cause, since I do all my commuting at night. I haven't messed with the distributor since I've owned the truck, but even so I need to adjust camshaft retard, last time I checked it was off a couple of degrees. But the MPG drop was pretty sudden, so I don't think that's the cause.

I didn't know about lubing the seal. If the filler neck isn't the culprit, I'll check it when I drop the tank. One thing that I thought of, I bought a new retaining ring from Advance this time around since the original was pretty crusty. Hopefully it's sealing properly.

On a 2 door, you don't have to drop the tank to replace the filler neck. Remove the wheel and plastic splash shield and you can get right in there.

Oh yeah I know, I just meant if I replace the filler neck and the code is still there, I'll be dropping the tank to check all the other possibilities.

Got around to checking things out to fix this P0455 code. I'm an idiot and just didn't seat one of the vent house connectors firmly enough when replacing the fuel pump. Had to partially drop the tank to get my hand in there. After driving around for almost a week waiting for the EVAP monitor to complete, tonight it did and still no SES light. Success. Thanks for the help.

Stuff happens;) Glad you got her fixed, and thanks for posting back.