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Author Topic: Vacuum Cut Valve Bypass Valve  (Read 8695 times)
jgaisior
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Vacuum Cut Valve Bypass Valve
« on: June 22, 2009, 12:50:50 PM »

Alright I have a 98 nissan frontier 4x4, and I my truck has had this code, P1491 (Vacuum Cut Valve Bypass Valve) on for about 6 months now. I haven't been too worried about it since it is still running as good as when I first bought it.

What I need to know is if it is important or a big deal? The only reason I am wondering is because I may be getting rid of it and would rather have the light off. But the little plastic valve is $135 and would rather not get it if I dont really need it, or atleast until I trade it in.
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OffroadX
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Re: Vacuum Cut Valve Bypass Valve
« Reply #1 on: June 22, 2009, 06:56:10 PM »

No worries, it's a minor emissions component to pull fuel vapor out of the charcoal canister.  Has no effect on the engine's operation.
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LastFronty
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Re: Vacuum Cut Valve Bypass Valve
« Reply #2 on: May 25, 2010, 12:50:30 PM »

 I'm just bumping this up to see if anyone has the part number for this valve?  P1491 Vacuum Cut Valve Bypass. $139 is not too bad. 
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OffroadX
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Re: Vacuum Cut Valve Bypass Valve
« Reply #3 on: May 26, 2010, 05:01:07 AM »

The problem may or may not be the valve itself.  Usually what happens is some of the charcoal gets sucked up the line and fouls the valve.  You might try removing it and blasting it and the lines out with some compressed air first.  Not sure if your 4-cylinder will have it in the same place, but the Evap Port shown here is the valve on the V6:

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LastFronty
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Re: Vacuum Cut Valve Bypass Valve
« Reply #4 on: May 26, 2010, 10:36:27 AM »

Thanks for the heads up on cleaning the valve and lines. The picture was also very helpful as I thought it was the valve under the truck bed above the spare tire. btw I'm working on a 2000 VG33e 4wd.
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OffroadX
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Re: Vacuum Cut Valve Bypass Valve
« Reply #5 on: May 26, 2010, 11:57:50 AM »

Ya know, I could be wrong about that actually.  There is another valve or two back near the charcoal canister.  The one shown is a frequent troublemaker though.
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LastFronty
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Re: Vacuum Cut Valve Bypass Valve
« Reply #6 on: May 27, 2010, 09:45:19 AM »

I cleaned and inspected the lines. I have yet to clear the code but once I do I'll report back if that was the fix. If not Iíll work on the lines by the charcoal canister under the bed. Thanks again. 
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Re: Vacuum Cut Valve Bypass Valve
« Reply #7 on: May 27, 2010, 03:36:57 PM »

I was just looking at the IACV-AAC Valve that is listed on Curtesy's website as part # 23781-D22U001 and I noticed my is not plugged into anything. Could this be what is tripping the P1491?  What and where would this plug into? 


Sorry for being such a nooob but all this has been very helpful. 
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LastFronty
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Re: Vacuum Cut Valve Bypass Valve
« Reply #8 on: June 10, 2010, 02:29:33 PM »

I found and fixed it! I had the timing belt replaced and the shop left off one of the vacuum hoses. So after cleaning all the lines with compressed air, I was just about to purchase the valve and then I found the open lines.   Thanks NOR et alia.
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