e9nine

I have decided to keep my Maxima and get her back to "new condition." (prodigal driver)

I had autozone pull up my codes and came out with Knock sensor (P0325), Vent control valve (P0446) & EVAP leak(P0440).

Knock sensor is a no brainer

Vent control valve: Do I have to replace the canister that goes with it too?

EVAP leak: Could this be related to the Vent control valve? Is there a hose that I should replace & how to test this.

Thanks in advance

e9nine

Found this after a little research, I know for a fact that it cannot be the gas cap. I have been driving the car now and everytime I fill up, the engine is off.... I do notice a little vacuum when opening the gas cap though (hmmmm) I guess it is time to bench test this sucker.

An OBDII car also monitors and tests the emissions system through the ECU. P0443 and P0446 are codes corresponding to the EVAP system. The EVAP system uses a charcoal canister to capture raw fuel vapors (hydrocarbons) from the fuel tank so they aren’t released into the atmosphere. The charcoal adsorbs hydrocarbon vapor, meaning the vapors are held on the surface of the charcoal and can be released by a burst of fresh air. When the ECU determines it should purge the canister, a vacuum is created that pulls fresh air through the carbon canister to the intake manifold. The valve opens and the vapors are consumed by the engine. The EVAP system is a non continuous OBDII monitor, only active certain times. A sensor in the EVAP system monitors fuel tank pressure to detect restrictions and fuel vapor leaks of no more than 0.04” in diameter in a hose or filler cap. These leaks can be caused by something as minor as a gas cap that hasn’t been tightened enough. However, Nissan issued several technical service bulletins regarding the EVAP systems on 1996 and 1997 Maximas. P0443 is the code for the Evaporative Purge Volume Control Solenoid Valve and P0446 is the EVAP Canister Vent Control Valve (Circuit). They control fuel tank venting air flow volume to prevent hydrocarbon's from escaping the fuel system and polluting the atmosphere. A properly functioning EVAP system consists of two functions- detecting leaks in vent lines and the hydrocarbon airflow purge from the canister to the engine. Your system is not properly purging the canister. Caused by water entering the hoses and corrosion and, believe it or not, spiders building nests in the vent tube, failure to the canister purge solenoid is common in these vehicles. The system was later updated to include a water separator which should be installed when replacing the solenoid to prevent further defects to the EVAP system. If the canister itself is not working properly, charcoal pieces may have obstructed the solenoid. There are 10 pieces to the package and not all of them may need to be replaced. A flow test of the canister purge valve and a pressure test of the EVAP system with the engine off can be performed to determine leaks in the fuel tank, lines, or cap and fix the problem. Although the EVAP codes don’t cause any performance issues, you will need to fix them if you want to pass emissions. While some OBDII codes only remain on until the system that failed passes a self-test on 3 consecutive trips, emissions problems need to be fixed before the code can be erased.

cassiejeffie

iTrader: (4)

Your vent control valve sticks open, causing leak and po440 code. Replace vent control valve and clear codes, you should be ok. The bad knock sensor will set a code but will not turn the check engine light on. Vent control valves go bad all the time.

♥cece*oaks♥

COOL.

Coolsaber57

iTrader: (22)

STOP BUMPING OLD THREADS NOOB.

DMaxima

I think there is a bulletin on nissanhelp.com about that problem

BORQUA79

Im having some drivability issues with a code for O2 sensor front bank 1 and the P0447. These codes wouldn't cause my car to hesitate on Drive, Reverse and 1,2 right????? At a red light the car seems like its trying to stall????

bebekhijau

is this charcoal canister can be disassemble? just curious want to see what inside it and how it works..

cashoit

O2 sensor shouldnt really cause it too hesitate. But elimate CEL issues and go from there man

internetautomar

iTrader: (30)

it can though, and as long as there is an obvious issue fix it first. many times have apparently unrelated issues been related.

Jeremiah Zampetti

Kinda doubtful that anybody will ever see this, but oh well. I got p0446 replaced my vent control valve after a few little tests and the code reset it's self after a few trips. Then I got to fixing my other codes (knock sensor and oxygen sensor) and then the very next day I got a evap leak code. So I looked under, found a broken tube that leads to the pressure sensor and I fixed that up. Then I got my trusty old p0446 code back. I have batt voltage at the valve. It's a new valve, So what could be my problem? The pressure sensor? All my other pipes seem to be in good shape but ya never know.

DennisMik

iTrader: (2)

The majority of the time the P0446 is a bad EVAP canister vent control valve. How new is that valve? These things are behind the left rear wheel and become corroded. There is a solenoid operated plunger inside it that becomes stuck and cannot slide back and forth.

Take the valve off and jumper power to it and see if the plunger inside moves. It should "snap" back and forth, not slide lazily. Sometimes you can free them up with WD40, but not always.

Jeremiah Zampetti

I'm

It's about 2 weeks old now. I pulled the old one and took it apart and it was corroded and didn't move easily at all. I tried to fix it up but I couldn't do I got new one.
Side note, what should the resistance look like on the pressure sensor?

DennisMik

iTrader: (2)

Sorry, I don't understand what part you are referring to when you say pressure sensor. But regardless, I don't know what the resistance of any of these parts would be. I would have to hope that it is in the service manual.

Jeremiah Zampetti

The "boost sensor" right next to the vent valve? I'll see if I can find the service Manual. Anyway I have a new one one the way that I found for cheap.

DennisMik

iTrader: (2)

Jeremiah Zampetti

The EVAP control system pressure sensor. And I found the service manual but it doesn't have resistance tests. Anyway, side note, with the vacuum cut valve, when I park there's a buzzing coming from it, I don't know too much about its functionality but that can't be normal

DennisMik

iTrader: (2)

When the engine is running, the gas tank has a slight vacuum in it. This is because the engine is sucking out the gas vapor fumes to keep them from going into the atmosphere. When you turn off the engine, the vacuum is slowly relieved and sometimes you can hear this happening. My 97 Max was pretty loud.

If you want to see if this is the case, remove the gas cap while the noise is happening. You'll hear a "swoosh" sound when you loosen the gas cap and the air rushes in to eliminate the vacuum.

Jeremiah Zampetti

Yeah i know. mine does swoosh when i take the gas cap off. So im lost at the moment. Ive no clue what to do now, i got my new pressure sensor but its the wrong one, thought i matched the number but oh well. I tested the resistance of that and it was really high as well. I may just try rigging it up to fit because the sensor body is the same, its just where it connects to hosing thats different. if you have any new suggestions or tests im all ears

Jeremiah Zampetti

Okay, update. I tested the vent control valve directly from the battery, it works. I test the voltage at the wire harness for the valve, i have batt voltage. I plug in the vent valve and nothing happens, but if i ground the valve else where on the vehicle, and use the + terminal from the wire harness connector, the valve will operate.

M in KC

I would pressure test the entire evap loop from the valve on top of the rear valve cover (EVAP purge volume control valve), with low air pressure and a squirt bottle of soapy water. When you take this valve off clean it if you haven't already. If you see anycharcoal bits in this valve you will need to replace your charcoal canister. When I was trouble shooting mine I inserted my air hose, (zip tied the blow gun partially open that I could remotely look for leaks) into the hose coming off the evap purge volume control valve to check for leaks.

unreal2k1

This might not be your case but I had this happen and it was the ground in the harness I peeled back the shields on the wires and found it was broken in two places. All this after replacing almost every component in that area. The positive wire never broke so when testing it on a grounding surface it read fine. and the neg was making contact when off the canister but when plugged in and the wire bent it lost the contact. Anyway worth a shot to see if the wire is broken coming down from the harness

Jeremiah Zampetti

I tested mine on a grounded surface as well as the harness ground itself. I found the same reading at both. I don't know how to tell if the valve supposed to grounded or not with key on engine off. But I get voltage. Now if I probe the valve, and use + from the harness and -from a ground on the frame, it works. But if I use + from the harness and ground on the harness it does not. Even though I get the same voltage readings from both areas.

Jeremiah Zampetti

Update. I bought a new ECM after sealing all leaks and testing all the components i could, I replaced the vent valve and vacuum cut cut valve. My new ECM throws a code immediately for the o2 sensor bank 1 sensor 2, for the sensor and heater circuit. Then after a short drive it will have p0446 in pending. Then another drive puts it in stored. I'm really at a loss for a fix. I've tried everything I can think of and it all tests good. And now I have 2 different ECMs giving me different codes.

surban1

iTrader: (17)

I hate evap problems! per pg 233 of ec section of fsm, it's either harness or canister valve, evap control system pressure sensor or blocked tube to the canister valve. my suspicion is if it were a harness issue, that code would come on immediately. so I'd check all vacuum hoses & fittings down and around that whole shenanigans back down there and then start looking at/playing with the evap control system pressure sensor (or its' connector & etc). good luck & don't give up.

Jeremiah Zampetti

I suspect harness but I can't tell. If I take a voltage reading from the harness positive and ground. It should be 0 normally right? Because the valve only energizes to test the system? I get battery voltage there but it doesn't activate the valve, but when I take + from the harness and ground it to the frame of the car it activates the valve. One more thing. If I unplug my ECM And ground the pin on the connector that leads to the valve, not the ECM, with key on it activates the valve. So that makes me believe the wiring is good. Maybe I purchased another faulty ECM. Who knows

bumpypickle

iTrader: (1)

Your investing too much time and money into this evap situation. If I were you I would invest in something like new CA bushings, ball joints, alignment, radiator etc.

surban1

iTrader: (17)

if I were you, i'dcheck all vacuum hoses & fittings down and around that whole shenanigans back down there and then start looking at/playing with the evap control system pressure sensor (or its' connector & etc).

Jeremiah Zampetti

It has to pass smog first. It runs well but I'm always uncovering damages from previous owners. I don't want to sink to much money into it then have it go. Alignment is next in the list though. And my radiator is good.

Jeremiah Zampetti

I've done that already but I'll do it again. I get the same reading off the EVAP pressure sensor as the sensor under the hood, right next to the intake. The harness has 12 volts at the sensor. I replaced a leaky vacuum cut valve. There use to be an audible leak coming from it

usurped

If this helps, so be it. Had P0440 all spring/summer, read threads and didn't want to spend big bucks to replace. Tried a spare gas cap and cleared light. Pop, light on two days later. Swap back to original cap.
Removed vent valve from above pic, and found corrosion, pintle seized. Sprayed and pried till it freed up. Light on again. Profanity. Drove for a month and pulled again, seems stuck so sprayed and pried again. Light off for a few weeks then on again.
Ignored till two weeks ago. When I removed it I found a small nick in the o-ring sealing the valve to canister. Found a spare from who knows what in my box of crap spare parts. Two weeks in and no light. I'm glad I didn't buy a $200 valve and hope it steers anybody else in right direction.

Jeremiah Zampetti

I'll just leave my solution here in case anybody needs it. I found a small crack in the vacuum line that connects to the purge control valve, at the same time I found a microscopic leak in the the t connector that goes to the pressure sensor by the charcoal canister. I can't say which one solved it but it may help to take a look at both.

maxprivate

iTrader: (12)

Glad you were able to figure it out. When i had that code I was able to free up the plunger for the canister, and I replaced the solenoid and one cracked vacuum line in the engine bay.. Code went away.

nissan99

the vent control valve what other years would it be the same part I got a 99 maxima ?

CS_AR

. The evap system parts for a 99 are different and in some cases more expensive than other years. Be careful on purchases to buy for a 99 only.