# (Sorry, it's another) P1448 Evap Canister Vent Control Valve Question



## David3000 (Feb 1, 2012)

My 1999.5 Pathfinder has thrown a P1448 Evap Canister Vent Control Valve (Open) message for the second time, so I am beginning to take it seriously. The first time I replaced the fuel cap because it was cheap and there are many suggestions that it can give a false reading (along with the P0440 message).

I pulled the Vent Control Valve off the canister and checked it. The o-ring is fine and when I apply power directly, it closes. When closed, it does not leak. I'm guessing that the system only applies power during a purge and I have no idea how to trigger that on demand, so I don't think I can test it in place. Also, there was no charcoal in the valve or hose.

I'm reluctant to drop a hundred bucks on a part that seems to be working. Any ideas about what to do/check next? Thanks.


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## Sam32 (Nov 3, 2012)

I have the same problem with my 2000 pathfinder. I'm getting the p0440 and p1448 codes. I replaced the gas cap and erased codes. they stayed off for 600 miles or so, but now they're back. I checked the Vent Control Valve and it is operational when voltage is applied directly. I think the canister is ok. there were some fine dust/charcoal looking particles coming out, but they didn't look like pellets like some others have described.

The vehicle was rear ended in the driver side a while back. I suspect this screwed something up, but i can't find it. Everything i have checked seems like it's working ok.

Did you ever figure out what was wrong with yours?

I'm a little reluctant to start replacing parts when everything seems to be working.


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## David3000 (Feb 1, 2012)

From what I have learned...

The VCV failure can be one of three things. One, the valve is bad. Even if it works when directly connected to the battery, remember that it is getting a full 12 volts and as much amperage as it wants. I don't think this is the case in line. The CPU may only be supplying the minimum amount required which may no longer be adaquite for an old part. I don't think most Nissan mechanics even know these values. They just see the code and replace the part. The only valid test seems to be the system test which, as you found out, can take around 600 miles to run.

Second, the wiring could be going bad. Electrical problems are nasty especially if they are intermittant. And third, the CPU could be malfunctioning. Either of these are going to be difficult and/or expensive to diagnose and repair. If you are getting about 10 volts at the VCV plug with the ignition on, this is the test for a closed circuit, not meant to trigger the valve. To me, this indicates that the wiring is not the problem. And if the purge test is running (occasionally), and the rest of the electrical system is okay, most likely the CPU is okay, or at least not the most likely cause.

Given all this, what I finally did was replace the valve, clear the codes, drive long enough for the other diagnostics to clear, and took it in for inspection. New York will fail it if there are any p-codes, but will allow one incomplete diagnostic test. Afaik this is because the purge test is so difficult to get to run that it is unreasonable to wait for it. Imagine your hourly wage mechanic driving around for 600 miles just to clear this test...

I haven't driven the Pathfinder much in the last 6 months, and I replaced the battery recently which reset everything again, so I don't yet know if the new valve solves the problem. But, I'm legal and I smell no fumes, so that's good enough.

If you do order a new valve, make sure you cross reference the original part number stamped on the side. Vent Control Valve and Purge Control Valve seem to be used interchangably even though they are not.


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## Sam32 (Nov 3, 2012)

Ok, here's an update.

I replaced the VCV and the canister. The valve did look a little gunky, so I figured it couldn't hurt. After a second inspection of the canister, it did have some charcoal chunks coming out, so it got replaced as well. Both of these things seemed to keep the SEL off longer (1500 miles or so), but it came back recently.

Seems like I could have an electrical problem. I'm not terribly interested in trouble shooting this one, and I don't know if I have the know how to do so. Any tips on inexpensive electrical troubleshooting this? I don't even know where to start.

The other thing is that the county I have the vehicle registered in does not require emissions testing, but a lot of the surrounding areas do require the test. That pretty much means I can drive it as long as I want, but can't sell it. I don't need to sell it now, but it would be nice to get it to the point where I could if I wanted.

Sam


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## smj999smj (Jan 1, 2006)

When the evap canister leaks charcoal, it contaminates the whole system and you will continue to get evap codes until every tiny piece is cleaned out. Nissan released a technical service bulletin describing the proper cleaning procedure. Here's a link to it:

http://www.aa1car.com/library/evap_nissan_ntb00-085a.pdf


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