So you got a P0448 code, which is a code for Evap System Vent Control Valve shorted. Have you checked the wiring?? Have you run any tests on the valve??

As far as returning electrical components, most auto parts stores won't let you return an electrical part once you have installed it. You may want to check with them before you do this.

 

The 2 wires going into the connector are intact and look good. The only test I did so far was to start the car and look for air flow out of or into the hose for the vent valve, with the valve out of the canister. No air flow or suction there and also no air flow or suction at the opening to the charcoal canister.

I want to test for 12 volts at the connector, but first I have to get it off. Struggling. Included some pics of the connector. Youtube videos say you just squeeze with thumb or with pliers, and pull off the connector. Ha.
Is it possible to use a flathead screwdriver to get the connector apart? I am able to get the tip into the slot. Hope the pics are useful.

Once I get the connector apart, I want to test the valve for a click when I apply 12 volts to it.

Thanks

 

Is it a locking tab for the connector about one inch west from your finger?

 

The connector I'm having a problem with is about 1 inch southeast of my fingertip. Not sure about a locking tab.

As far as getting the valve back into the canister, I'm going to try removing the O ring, temporarily, just to see if the 'less tight' fit will allow me to get deep enough into the canister to lock the valve in place when I turn it clockwise.

 

It will lock but likely leak to make evap code at the tank pressure checks the computer makes on regular basis. Don't use silicone or RTV there as fuel vapors eat silicone. You blow through valve to make flow, there is none to present there otherwise. The unit powered up will block flow or allow it based on power on or off.

The plugs tend to get hard at the lock tab to not come loose. Best tool I ever found to remove them is cheap harbor freight long nose needle nose pliers with the outer 1/8" of tips bent down toward each other to get the lock tab pressed down inside the hole.

 

Update: I removed the O ring on the vent valve, and now it can get behind the tabs of the canister port, and lock in place. It even clicked into the holder. Of course I'll have to put the O ring back on to do it right, but at least I know it fits in nice and tight. I thought it might be loose since one of the 4 tabs on the valve spout broke off.

Would silicone grease on the O ring make it easier to squeeze down?

Still can't get the electrical connector apart. Could it be stuck due to corrosion inside? Can I work some sort of dielectric cleaner inside it to loosen things up in there?

 

Don't be surprised if the o-ring leaks at putting valve back in. The application there seals in an odd manner, the o-ring does not seal on the OD but rather on the sides which a broken tab may well not seal. The easiest way to get back together is a new softer o-ring to squeeze down easier. BTDT. Trying to make a harder (fuel vapors make the rubber harder) o-ring compress can break more tabs off. Grease will not soften a hard O-ring.

The electrical plug is purely a plastic problem that almost all Nissan connectors can do. The tabs firm up to not be able to depress quite as far as they did new. Compress the tab enough and it WILL come loose. Why I made a $4 tool that does it instantly.

While at it shine a light inside the valve to see if it is nice and shiny inside or rusted or corroded. Either of the latter is considered a bad part and sign the o-ring was already leaking.

 

Finally got the connector apart! I used a small vise grips. Had to go at it from the side. Didn't have to press very hard. Just squeezed and wiggled, and it came out with a little puff of dust. THe vise grips had that bend at the ends of the pinchers that was just right to press only on the right spot.

AMC49, it looks clean inside. Looking inside the port that snaps into the canister, I can see a spring and yellow shaft going up the long part of the valve. I assume the spring is pushing the piston up to keep the hole open, and when the computer closes it, the piston gets pushed down to seal the valve.

I can blow through it in both directions easily. It's a normally open valve, so that's good.

I want to apply 12 volts to it to see if it closes, and what the seal inside looks like when closed. Have to figure out how to do that. Maybe put jumper cables on my car battery, then hook smaller wires to the cable ends.

 

You could use a 9V battery from a home smoke detector.

 

Careful there close to canister vent pipe, if the harness holds part close. A spark there would have a longshot at a fire but it IS possible.

 

I have the valve off the car, so it is not near the canister. Going to get some alligator clips at Harbor Freight, and use the jumper cable method tomorrow. If the solenoid clicks and closes the hole up, which is what it is supposed to do, I'll put some plumber's grease on the O ring, and see if I can get the valve back into the canister, hook the connector back up, and see if the code goes away. If it doesn't go away, I'll order a new valve from Amazon or Ebay, for $32. Can you believe the valve is $61 at Autozone? Even $32 is outrageous.

 

When it closes blow in it, even a slight leak will pop a code.

 

Update: got 12 volts from Versa battery to test the valve. Disconnected both cables from the battery first to be sure i would not affect the V's electronics if the pos and neg on my testing leads accidentally connected !

* Got the click sound. * Blew into both tubes, no air at all getting through. Nice tight seal.

I left the 12 volts on the valve for like 2 or 3 minutes, and it got warm. Hope I didn't overwork it.

So the valve tests out 100% OK except for the possibility of a leak at the O ring due to one tab being broken off the tube going into the canister.

The internals of the valve were very clean. Inside of electrical connector was also very clean. Going to lube the O ring up with plumbers grease then try to get it back into the canister, and see if the code comes back.

I made myself some notes on how to get the electrical connector off, so I don't spend as much time on it next time.

If the code comes back, I suppose I'd have to buy an new valve simply for the 4th tab, and try it out.

 

ANOTHER UPDATE: I got the valve back in by using lots of spit on the O ring. It went right in.
Reconnected the electric connector. Started the car. I was expecting to have at least a few minutes of no code, since I had disconnected the battery, but the SES light came on after 2 seconds.

Another piece of evidence : I took off the gas cap to see if my spare gas caps would fit, and I noticed that cap did not click or resist opening at all. It was loose ! Maybe it's been the cap all along. I will check the cap again after some driving to see if it loosens up again. My gas door has become bent all by itself, so there seems to be some structural forces at play around the gas cap. Maybe it loosens up while driving. When I get gas, I make sure it is tight, and always hear at least on good click. But looks like it loosens itself up later.

 

One click is not enough, you spin it to get several clicks. Not doing so is why it comes loose, the several clicks is a torquing thing. The cap should never click undoing it or the rachet is dying.

 

A bad gas cap can do strange things. I think I would get a new OEM gas cap and see if that helps.

 

Rebuild them and easy enough, just a one way check valve inside. I do radiator caps too.

You have to know that the cap seals by the torque compressing the gasket. One click is absolutely NOT that. Not once the seal gets harder with age. The harder it is the more the gasket has to be sunk into and at one click you are already loose. I go a half turn of clicking and zero issues ever with gas caps on a long stream of cars. I have never bought a cap except when somebody broke mine to pieces while stealing gas. The new cap leaked but I rebent the sealing flat where the burglar tool screwdriver dented it and then new cap worked for years after that too. Simple idiot science there. Most of evap system science is once you understand it.