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How I fixed P0448 for free (dust clogged EVAP cannister)

 
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Aerodan



Joined: 13 Apr 2016
Posts: 6

PostPosted: Tue Jan 23, 2018 11:18 am    Post subject: How I fixed P0448 for free (dust clogged EVAP cannister) Reply with quote

I was intermittently getting P0448 for months. Eventually I was getting it continuously. (As in, I'd reset the engine codes, and I'd get P0448 again within a day or two.)

I was completely uneducated on the EVAP system at first, so I wasn't sure what was going on or how to fix it. I googled around on this forum and didn't find a solution, so I'm posting my solution because I'm sure others occasionally run into this. Furthermore, I read emissions system description in the service manual. That was educational. I also read the diagnostic procedure for P0448 in the service manual. That was useful.

The root cause of the problem was dirt getting into the EVAP system's charcoal cannister. If you search around enough, you'll find Nissan has a service bulletin (reference NTB07-060a) for installing a filter kit (part number 14953 – ZP80C) on the vent hose of the EVAP cannister. The bulletin basically hints at dirt clogging up the EVAP cannister as being a potential source of codes P0442, P0448, P0455, P0456, and P1446.

For the most part, I followed the diagnostic procedure for P0448 in the service manual. I tried replacing the vent control valve on the charcoal cannister. That was a waste of $40-some dollars because it fixed nothing.
After that, I basically got to the point where the manual said to replace the charcoal cannister. I shopped around for charcoal cannisters. I thought their price was ridiculous. Before forking out the money for an overpriced used charcoal cannister that I wasn't even sure was going to fix my problem, I tried blowing the dust out of my charcoal cannister first. That fixed my P0448 code. Here's how I blew the dust out...

I removed the charcoal cannister from the vehicle. It wasn't easy. I had to drop the spare tire to get to it. I was able to remove all hoses and connections before I removed it. Disconnecting some of them was a real pain in the ass, but I fandangled the cannister around enough to get access to each connection and get each disconnected (hoses and electrical connectors). I removed the charcoal cannister with the vent control valve in place. Once the charcoal cannister was out, I removed the vent control valve. Be careful trying to remove the valve. There's a locking mechanism on it that will only allow it to pull out when its rotated at a certain angle. If you pull too hard, you'll break the tabs on the locking mechanism, which is exactly what I did. Going off of memory, the valve needs to be rotated counter clockwise about 45 degrees to remove it. (Counter clockwise when looking down on the top of the cannister.) Even when you have the vent control valve rotated to the correct angle to release it, there's a rubber o-ring that'll grip that sucker in the hole pretty tenaciously. It takes just the right tough to know whether one is not pulling hard enough versus pulling too hard if the valve isn't rotated to the correct angle. Unfortunately, removing the vent control valve was necessary for me to clean my cannister out because it is a lack of airflow through this port that caused my P0448 code. (I was able to make an educated guess about that my studying the evap system and the P0448 code in the service manual.)

Anyhow, once the cannister is out of the vehicle and the vent control valve is removed, I reattached the short gas tank hose. The gas tank hose I'm referring to is a 4" long hose with a 90 degree bend. It's the hose that attaches NOT to the vent control valve, nor the port in the middle of the cannister, but rather the port right next to the electrical connector for the pressure sensor (which is the only port left on the cannister). I then put my finger over the port on the middle of the cannister, took a deep breath in, and blew into the gas hose as hard as I could! I was able to see a puff of very fine dust come out of the vent control valve port! I turned the cannister upside down and somewhat gently shook it to try to get dust to fall out of the vent control valve port. I then went back to plugging the middle port and blowing into the gas hose as hard as I could. I also turned the cannister upside down when blowing into the gas port so gravity would help pull the dust down out of the vent control valve port. Every couple times I'd blow into the gas port, I'd shake the cannister upside down to let dust fall out.

A couple things to note:
1. Close your eyes when blowing so dust doesn't blow into them.
2. Blow as hard as you can!
3. Don't breath in through the gas hose or anywhere near it!!! When you breath in, move you head away from the cannister. You'll wind up huffing gasoline. You'll quickly see the first time you try.

I kept doing this for as long as long as I could stand. After 15-20 minutes of blowing and shaking, I was sick of blowing into the hose and only a tiny puff of dust was coming out, so I called it quits and put everything back together. I reset the codes by putting the computer into the diagnostic readout mode and holding the gas pedal down for 10 seconds. The code never came back.

I drive on a lot of dusty roads. The problem was only going to reoccur if I didn't do something to prevent it. Going off of memory, I want to say the filter kit was a $100-some dollars and an annoying bit of effort to install. Instead, I basically extended the vent control valve hose up to the engine bay to prevent it from sucking in dust from the road. I bought 12 feet of hose from O'Reillys and a plastic coupler to join the existing preformed vent control valve hose to my new hose. (I can't recall what size hose and coupler I bought. I think it was 1/2 inch? I asked the O'Reilly's guy if I could have a few inches of 1/2" hose for free to test fit before purchasing everything.) I kept the existing vent control valve hose simply because I liked the nice preformed bends in it. I wasn't sure if my new hose would kink if I tried to bend it around in place of the existing hose. I coupled my 12 foot section of hose to the existing vent control valve hose and ran it under the vehicle up to the engine bay by the brake booster. I had to squeeze the new hose into some tight spots to secure it under the vehicle, but I think I got it situated so it's protected from wear and tear from the road. I haven't had an issue in the last 3-4+ months of driving, so fingers crossed I fixed the P0448 problem.

Hopefully this helps anyone experiencing P0448 or potentially P0442, P0455, P0456, and P1446.[/img]
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BullDozer



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PostPosted: Wed Jan 24, 2018 7:25 pm    Post subject: Reply with quote

Thank you for taking the time to post this with all your details. I learned something new.
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smj999smj
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PostPosted: Thu Jan 25, 2018 10:52 pm    Post subject: Reply with quote

It's amazing how much dirt and dust can build-up in and around the canister area. Another great idea sticking it in just behind a plastic panel in the rear wheel well! Thanks, Nissan engineers! Rolling Eyes
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palmerwmd
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PostPosted: Tue Feb 20, 2018 5:49 pm    Post subject: Reply with quote

Thanks for posting this!
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smj999smj
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PostPosted: Tue Feb 20, 2018 8:09 pm    Post subject: Reply with quote

I just had a similar issue on my 2008 Pathfinder. At 220,000 miles, it kicked the P0448 code. I replaced the original canister check valve with the updated part and flushed the dirt out of the vent hose and filter with water. A couple of days later, the code came back. I had a feeling it was dirt in the canister so I purchased a new one (OES brand) from Parts Geek for, if I remember correctly, $157 (cheapest price I could find). I was surprised when I got it because it turned out to be a genuine Nissan canister in Nissan packaging! I weighed the new canister and it was 3 lbs. 1.1 oz. I removed the old canister and it weighed 3 lbs. 10.5 oz., so it was definitely full of dirt! I tried shaking it upside-down but not much came out. I installed the new canister, erased the code and a week later, knock on wood, no more code!
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grm3



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PostPosted: Fri Feb 23, 2018 10:41 am    Post subject: Reply with quote

Besides the P0448 code, did you also have trouble filling the gas tank?
I had this issue a few months ago with the code and trouble filling the tank. I had the vent valve replaced (with the old style though, since it was cheaper), and that seemed to fix the problem. Everything has been fine, but now I just got a text from my wife saying she's having trouble getting gas.
Now I'm thinking the canister may be the problem.
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smj999smj
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PostPosted: Fri Feb 23, 2018 2:48 pm    Post subject: Reply with quote

I didn't have any problem filling the tank, however, that is often the symptom of a canister check valve that is stuck closed or a clogged vent hose.
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grm3



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PostPosted: Fri Feb 23, 2018 4:36 pm    Post subject: Reply with quote

Well, there's no check engine light yet, but there is a pending P0451 code.
I'll try filling up tomorrow.
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grm3



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PostPosted: Sat Feb 24, 2018 10:46 am    Post subject: Reply with quote

I was able to fill up today without a problem. Hopefully it was the gas pump yesterday and not the truck.
I'll have to see if anything comes of the pending code.
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smj999smj
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PostPosted: Sat Feb 24, 2018 11:48 am    Post subject: Reply with quote

P0451 is for the EVAP system pressure sensor, which is mounted to the canister. It sets when it detects pressure in the purge system. This makes sense considering you had difficulty when filling the tank. If the vent for the canister was closed off by either a stuck-closed valve or clogged vent hose, it could cause both the code and the difficulty filling.
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grm3



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PostPosted: Sat Feb 24, 2018 3:39 pm    Post subject: Reply with quote

Thanks for the insight, smj. Your posts have been very helpful over the years.
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CAMO



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PostPosted: Mon Feb 26, 2018 4:22 am    Post subject: Reply with quote

I used a small pump


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PostPosted: Tue Mar 13, 2018 1:15 am    Post subject: Reply with quote




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