CEL codes P0325 and P1491

[csutke]

So Im in texas for work, out in a natural gas drilling field and today I got a little but of of break so I decieded to go to town and get some food and supplies. On the way there I noticed that my CEL was on. When I got to town I had the "helpful" people at autozone pull the codes for me. 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. If anyone can help it would be great to get this figured out so next time im in town I can get the correct things to fix it.

 

Thanks

[revgolem]

its an EVAP code. most manufac. call the "Vacum cut valve bypass valve" the "purge" valve. it opens to allow manifold vacuum to evacuate the gas vapors in the EVAP canister as part of the required procedure to test the fuel system for small leaks (as small as 0.020") it sends the vapors into the intake and then uses the O2 sensors to calculate the amount of vapors that were purged. something happened to cause the ECM to not see the vapors it was expecting. valve could be stuck closed, lines blocked... etc. could also be a source of the knock code depending on how its reacting to what it thinks it sees.

 

neither code should cause a problem driving, only prevent you from passing emissions depending on local laws.

 

on a side note, what part of TX are you in? I moved to WA from Austin about 3 years ago and have been wondering whats been going on back there.

[csutke]

right now im outside of fort stockton at longfellows ranch, but hopefully i wont be here to much longer.

 

So if I wanted to fix the problem how would i got about doing this? whats involved?

[revgolem]

i was going to c opy/paste the test procedure from ALLDATA, but it's a huge long mess of text/images from a secure site. below is a portion that i think may apply. it's not so much that the procedures are hard, but the system is so complicated that without a detailed understanding of exactly what is going on when the ECM runs it tests that many experienced machanics loose their hair trying to solve these problems. ill try to do some research in the next day or so and see if i can find something more (if someone else doesnt beat me to it)