Hello everyone,

This past year I replaced all my o2 sensors and y-pipe due to CEL light indicating 2 of my 4 o2 sensors were shot and the y-pipe has a crack in the flex, so I did them all... now.....

The CEL came back on and the code read p0440 from the ODBII scanner. Doesn't mention O2 sensors thankfully, but it says small EVAP system leak or something...

About 6 weeks ago, I gassed up about 10.00 worth at the local Shell with the high grade and got on the highway, and about 20 miles down the road my CEL came on. I got gas the next day and drove about 30 miles and the light went off. I'm figuring it was the gas cap that I didn't tighten enough without realizing it. So no worries.

The CEL came back on about a week ago, and I made sure the gas cap was tightened up nicely, but the light still has yet to go off and I've gone about 300 miles.

Could this be as easy as a bad gas cap? Original Gas Cap (137k miles) or could I possibly has a bigger problem and need to replace the EVAP Canister purge Volume Control Valve?

(( also the other code that the reader found was p0325 - knock sensor, but seeing how I have fat fingers, and can't reach the KS, i'll have to pay the stealership the 600 or so to replace that soon. ))

 

so what codes do you have this time around?
and don't pay the dealership $600 for KS.
i went to my mechanic and he did it for $130, code was gone when i got home.

 

Indeed, you never made it clear on what codes you have now.

$600 for doing the KS? Seriously? Come to TN, I'll do it for $300

Why do you assume it's the EVAP CPVCV? Do you have a code for it, or are you assuming it from the P0440?

 

Sorry, same code

p0440 - evap small leak
p0325 - knock sensor

but I went to the dealership and got a new nissan cap for 18.00 this morning. drove around a bit today running chores, and the light when off this evening. Hopefully that was the true problem and the code and light stay away. Stil lshows p0325 however which is the KS. but that's another issue to work on later.

 

Unfortuantly, the same code just returned today.. p0440. other than the knocksensor code, that's the only one the OBDII reads.

What might the other possibilities be that I would need to replace?

 

Don't just start throwing parts at it, you need to do some actual diagnostics.

There are a lot of things that can cause P0440.

Code: P0440 | Description: EVAP Small Leak

 

so in other words.. take it in the shop for diags? LOL

 

If you don't want to do it yourself, sure.

 

I would check the tightness of the gas cap before anything, especially if other people drive your car and are nice enough to add fuel. Get at least 3-5 clicks onto it. If its tight, loosen it and see if there is a feeling of a pressure release, there doesnt need to be a sound, but a feeling like as if you were opening a plastic bottle. If no pressure, clean it, and add a little vaseline around the rubber ring at the base of the threading (inspect this area). If there is still no seal, spend the 5-10$ and get a new aftermarket (I recommend Stant) gas cap- assuming the gas cap is a flimsy looking culprit.

I had the same code, but it was obvious because the problem was intermittent, sometimes throwing a code 1/4 ways through a tank, sometimes not. Until finally, the code was constant and the cap just wouldnt pressurize.

 

I got a new gas cap the other day, and the light did go off, but it came back w/ the same p0440 code. I'm going to guess it's something other than the cap.

 

checked my codes again and now I have the p1448(EVAP canister vent control valve)

does anyone have a picture of the EVAP canister vent control valve and it's location? During searching, many people are saying by the the throttle body, and others say behind the rear drivers wheel so I don't know which place to look and what it looks like.

1999 Maxima SE ( Cali Spec )

 

 

thank you

 

I just bought a 97 GXE and it is throwing a few codes at me, one is for the upstream o2 sensor and I am also getting the EVAP canister vent control valve and another control valve (I think it's the purge canister, I don't have the info in front of me) I'm not the most automotively literate person, would either of these cause the other?

 

Had a similar issue with my Maxima years ago. The EVAP canister vent control valve was sticking due to rust on the shaft of the solenoid. Cleaned the shaft with some sand paper and lubed it a little. Have not had an issue since. Hope I did not jinx myself.

 

I literally just replaced this in my GF's 97. Easy to replace, but its actually pretty expensive for what is. Dealer quoted me $145 just for the CVCV.

I hope you have better luck than I do w/ the bolts that secure it to the EVAP Canister. Mine were rusted in and I couldn't get one out...it just spun in the bolt hole I ended up having to get a CVCV and a new Canister.

I'd definitely try cleaning/lubing the shaft (no homo ) first.

 

Thanks for the advice, I'll let you know how it goes

 

What effect is a sticking EVAP solonoid going to have on my MPG and performance of my car? Is it really worth worrying about?

 

Only worth worrying about when you go for emmisions testing or if you want to sell the car. Personally, I just don't like driving a car with the CEL on.

 

The late model 4th gen evap system design is a joke. The vent control valve, along with the vacuum cut bypass valve, are "used only for diagnosis" - meaning they open and close to allow pressure to build up so the system can diagnose if there is a leak/evaporative loss. The 'detectors' that compose this 'leak detector system' do nothing but acknowledge their own leaky broken existence, causing the very problems they are designed to detect. Its the equivalent to having a smoke alarm that causes fires.

 

hey pmohr,
That pic you posted showing the EVAP Canister Vent Control Valve is great, any chance you got one showing the EVAP Canister Purge Volume Control Valve? My Haynes manual sucks.
I'm throwing codes for both (P0446 and P1445) and want to check them out this weekend.
Thanks

 

 

Thanks,
that makes things much easier. Where do you get those drawings? If you don't mind my asking.

 

The FSM.

 

i got the same code, no idea where to even start with it, i changed my gas cap but its still coming back once in a while

 

Anyone know where I can buy parts for the EVAP system? I tested my Canister Vent Control Valve and it worked a couple times, now nothing. I have checked the sites of every parts store I can think of and can't find one anywhere.

 

Hey Nopike,
How did you get the valve apart? I got mine off and don't see any way to open it.

 

You don't need to take it apart. IIRC when you apply 12 vdc to one pin of the valve and ground to the other pin (where black wire goes) the shaft should come out of the valve or you should be able to just pull the shaft out by hand. You should hear the valve opening and closing when you apply the voltage. It has been a few years since I did this so I don't rememeber exactly how I did it but I know it was pretty easy to clean the shaft. The shaft had rust on it and it was obvious it was not moving freely.


You want that valve to open and close easily when voltage is applied, if it gets stuck you get that evap code. See what you can do to clean it. The valve is available at http://www.courtesyparts.com/ I could not locate the valve on the website but they sell it, call them. If your valve operates smoothly and looks good it is probably OK

 

Guys. Im getting the P0440 code.

A few weeks ago I got the P0446 code and replaced valve. Fast foward a few weeks, and now Im getting the P0440 and KS code. New KS is on order. Im not sure what to do about the P0440. Freakin EVAP codes suck.

I thought maybe I got a faulty new valve, so I tested it and applied 12V. The valve is working fine. I dont think its any of the other EVAP valves/sensor since the CEL would illuminate for a faulty sensor/valve.

I havent replaced the gas cap, but ima check for air release per FSM diagnostics. Might just buy a new gas cap anyway but i think my gas cap is good. Honestly, I can sometimes smell gas around the outside of my car. Not too bad, but its there. Maybe my filler neck is rusted to bits. Ima check that too.

Any other suggestions?