P1491 Vacuum Valve cut bypass valve

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04LEMASS
Posts: 97
Joined: Wed Mar 07, 2012 4:59 pm
Car: 2004 Nissan Pathfinder LE Platinum
-K&N Air Intake

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Ive got this service engine code : P1491 and it says Vacuum Valve Cut bypass valve. Not exactly sure what i means, maybe it has to do with the evap canister. Could it be from a bad gas gap? Could it be related to my k&n air intake?


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Towncivilian
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Car: 2001.5 Pathfinder SE 3.5L 2WD A/T
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It could be something as simple as a clogged hose. Remove the hose and check.

Image

Other potential causes:
  • Vacuum cut valve bypass valve
  • Vacuum cut valve
  • Bypass hoses for clogging
  • EVAP control system pressure sensor and circuit
  • EVAP canister vent control valve
  • Hose between fuel tank and vacuum cut valve clogged
  • Hose between vacuum cut valve and EVAP canister clogged
  • EVAP canister
  • EVAP purge port of fuel tank for clogging
If you ever "top off" the fuel tank after refueling, stop doing that as it allows excess fuel to enter the carbon canister and damages it. Stop at the first shut-off click.

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04LEMASS
Posts: 97
Joined: Wed Mar 07, 2012 4:59 pm
Car: 2004 Nissan Pathfinder LE Platinum
-K&N Air Intake

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Okay whats a good way to check if their clogged?

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Towncivilian
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Remove them and blow into them with compressed air to clear any clogs.

Yazir
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Joined: Tue Jan 15, 2013 12:40 am
Car: 1998 Nissan Pathfinder LE - Mahogany Pearl
Location: Reno, NV

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Sorry for reviving this old thread, but TOWNCIVILIAN, I got the P1491 code 50 miles after I topped off my fuel tank. Any ideas on what can I do to solve the issue, which is most likely what you just said, "excess fuel in the carbon canister". This is only the first time that I put gas on the truck ever since I bought it.

Anyways, I just want to know if I should just wait and see if the SES light comes back on (I reset it today with the code reader). By making the mistake of topping off the tank just once, is it a problem that may get fixed by itself (evaporation?) or should I start looking into reaching the canister and cleaning it with compressed air?.

Thanks.

Yazir.

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Towncivilian
Posts: 4995
Joined: Sun May 23, 2010 10:21 am
Car: 2001.5 Pathfinder SE 3.5L 2WD A/T
2007 Altima 2.5L CVT
2012 Sentra 2.0L CVT Special
2012 G37 Sedan 7A/T
Location: Florida, USA
Contact:

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If the code has been cleared, drive around for a while and see if it reappears. If it does, on we go to diagnosis. :)

Yazir
Posts: 11
Joined: Tue Jan 15, 2013 12:40 am
Car: 1998 Nissan Pathfinder LE - Mahogany Pearl
Location: Reno, NV

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Thanks a lot. I'll let you know.

Yazir

sammy6
Posts: 4
Joined: Fri Dec 30, 2016 4:08 pm
Car: 2002 nissan pathfinder

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I had a 1491 error code drive me crazy...first I replaced the valve cut bypass solenoid...still had error code.I then replaced the the valve cut bypass valve (four hoses going to it) with a used one from junkyard...same problem.Took apart valve cut bypass valve(popped the top off with small slotted screw driver) and cleaned inside which had debris in it,seemed to be rust or small granules inside.... still error code 1491.
Read post about blowing air through hoses and whala...no air coming out of or between valve cutoff bypass valve and evap charcoal canister. The line that was plugged solid with rust was a hose coming from bypass valve that split off to a hard line that was routed through wheel well (looks like a brake line).
The line itself looked brand new on the outside but again was plugged solid from rusting inside out. Replaced the line with one I made and the trumpets started to blare in the sky with approval. Finally the fix!!!!!!!!!!! .
I'm convinced others are having the same problem I have experienced seeing that hard line portion coming from the cutoff bypass valve is being restricted with rust seeing it is exposed inside the driver side rear wheel well of vehicle. I hope this helps others. Good luck!


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