csutke Posted April 2, 2008 Share Posted April 2, 2008 About a three weeks ago in the gas fields in Texas I was driving into town to get some supplies and what not and noticed that my CEL was on. Had the people at Autozone pull the codes and heres what came up: P0325 and P1491. They said that P0325 was the knock sensor and I knew about that as Ive it the CEL trip for that before, but the other code P1491 was new to me. The definition from them is: Vacum cut valve bypass valve. Problem causes: Failed vacum cut valve bypass valve Blocked line. They couldnt help me firgure out what the problem was or where it was at. I have found this valve in the FSM but cant seam to find it on the vechile. Also could this cause the code for the knock sensor or is the knock sensor actually bad? If the knock sensor is actually bad do i really have to take the intake off to change it? If I do have to take the intake off how hard is it, and is there anything that I should be aware of as Ive never taken it off before. Thanks Link to comment Share on other sites More sharing options...
94extreme Posted April 2, 2008 Share Posted April 2, 2008 related info Link to comment Share on other sites More sharing options...
k9sar Posted April 2, 2008 Share Posted April 2, 2008 I have never seen the knock sensor actually go bad. Usually there is a different problem that makes your truck try to overcompensate for and run sh!tty, thus causing the knock sensor to detect. Link to comment Share on other sites More sharing options...
tmorgan4 Posted April 2, 2008 Share Posted April 2, 2008 I have never seen the knock sensor actually go bad. Usually there is a different problem that makes your truck try to overcompensate for and run sh!tty, thus causing the knock sensor to detect. Nissan knock sensors are NOTORIOUS for going out. Most people don't bother replacing them since it apparently doesn't affect engine performance on the VGs. Link to comment Share on other sites More sharing options...
k9sar Posted April 2, 2008 Share Posted April 2, 2008 Nissan knock sensors are NOTORIOUS for going out. Most people don't bother replacing them since it apparently doesn't affect engine performance on the VGs. well... there ya go. Link to comment Share on other sites More sharing options...
ennacac Posted April 2, 2008 Share Posted April 2, 2008 On the Xterra forum I don't think there was anyone on there with a knock sensor that was working properly. They are under the intake if you really want to change them. Tom Link to comment Share on other sites More sharing options...
csutke Posted April 2, 2008 Author Share Posted April 2, 2008 so could the other code be causing the knock sensor code? if i do change the sensor will it change anything at all or will it not do anything? If I do change it is it nessecary to pull the intake or can i get to it without pulling it? Link to comment Share on other sites More sharing options...
94extreme Posted April 3, 2008 Share Posted April 3, 2008 it may for a while.. i don't know if it's actually the sensor or a glitch somewhere. i'm pretty sure it's a PITA to do the exchange, thus no one does it as there seem not to be any negative effects. noticeable ones anyway. Link to comment Share on other sites More sharing options...
vengeful Posted April 3, 2008 Share Posted April 3, 2008 the vaccuum cut bypass valve code will NOT trigger the KS code. It is a separate issue altogether. Forget about the knock sensor for now and concentrate on the bypass valve. Symptoms of a bad bypass valve include a rough high or low idle speed or an unstable idle. Possibly a pinhole leak in the line too. Have it checked by an emissions specialist. Pardon my speelijg and grammar, I'm mobile. Link to comment Share on other sites More sharing options...
csutke Posted April 4, 2008 Author Share Posted April 4, 2008 Could you direct me to the location of the valve, I cant seam to find it. I dont seam to be having bad or rough idle though. Link to comment Share on other sites More sharing options...
vengeful Posted April 4, 2008 Share Posted April 4, 2008 Yeah, no....I have no idea. LOL. I've got the same code, along with about 13 others...I'm just going to milk this thing until I find another one, and say good riddance. Link to comment Share on other sites More sharing options...
nissandoms47 Posted April 4, 2008 Share Posted April 4, 2008 You probably are not looking in the right place.. The valve is located in the rear of the vehicle right above the panhard rod, in front of the spare tire. Somewhere in that general area. Link to comment Share on other sites More sharing options...
chappy Posted April 4, 2008 Share Posted April 4, 2008 It sits on the shelf just forward of the canister you can follow the lines from the canister to it. There are two bolts holding the shelf to the body kinda hard to see with the shelf in the way so just pull it down. I have had the same code for a while comes and goes. I don't know how much the part is looks easy enough to swap though. There is a tsb to check so I'll try to find it when I get a second. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now