Check Engine soon

[black2blackQX4s]

So I had a friend use his ODBII reader check my codes.

I got one known : P0158 which is a sensor.

But the other code it threw was P1491

I did not see that in the FAQ list. Any ideas what it could be?

My exhaust has a leak in it and I am guessing it all relates to this. Any sources for cheap exhaust products for the 2002 qx4?

[Chuck Tribolet]

On my '01, P1491 is Vacuum Cut Valve Bypass Valve.

[Empty V]

I did not see that in the FAQ list.

Because it's not there, look in the 3rd thread down called ODB II Code Chart

Billy

[black2blackQX4s]

Yeah, I'm sorry I was referring to that thread. The first code is included, but it doesnt go far enough to include the second I found.
Cool rack!

Chuck, is that difficult to fix?

[Chuck Tribolet]

Dunno how hard it is. I've never had it fail (and I think my stick doesn't have one).

[vannaksao]

I have a P1491. How do we get it fixed? The came on about a year ago, mechanic said the exhaust leak in the back was destroying the sensor. He replaced the sensor and the light went away. Exhaust leak came back, and the p1491 came back on. Logically, one would think to go back to where it was fixed- but I want to do it myself. Someone said the sensor in the engine bay though, close to the intake. not sure...?? Help?

[vannaksao]

P1491 is not the EVAP Service Port you're refering to; though, it is part of the EVAP system and should also be inspected. P1491 directly relates to the Vaccum Cut Valve Bypass Valve (vc/v bypass/v). The vc/v bypass/v sits in between your gas tank and the EVAP Canister. I've included a link that shows what the vc/v bypass/v looks like. I'll be ordering this part next week, and I'll keep everyone updated.

The picture:

If you are on your back, underneath the car, you'll be able to notice the vc/v bypass/v bolted the a bracket. Remove the two bolts that attach the bracket to the car, and then remove the bolt that holds the bypass valve to the bracket. This is what you will see

http://s1193.photobucket.com/albums/aa3 ... s%20Valve/

The part is about $113 bucks.

[scrotuss]

I'm dealing with a P1491 DTC as well, and it's been a b****. I replaced the canister pressure sensor and the vacuum cut valve (the white plastic one shown in vannaksao's photo) because mine was MELTED. Now, I still get the P1491, but also, my fuel tank does not vent at all (definitely extinguish all flames prior to opening gas cap). I re-checked my bypass valve, which originally seemed OK, and I notice it tends to hang-up in the energized position. Vent lines and canister all seem clear. I guess it's time to replace the bypass valveand hope for the best.

[vannaksao]

Yes, change that and you'll be all set. Let me know if you or anyone needs an EVAP Service Port. Brand New OEM. Pics and diagram below:





-Vannak