High Pitched noise from dash ?? P0452 ??

I need your help. I have a 2000 GMC jimmy with 200K 4.3L. The 4x4 has been working intermittently for the last year (typical, eh) Today I noticed a high pitched 'ringing' noise coming from the dash area. This noise is constant, while driving, and even when the truck is off. I even unhooked the battery (it kept on rining) let the truck sit for a half hour...it kept right on ringing. I have no clue what this could be...anyone ever heard of this before? My engine light has been on for the last couple days, which I figured was a typical misfire that I get occasionally. I put it on the code reader and it gave me a P0452 Evap emmission sys pressure sensor/switch low input. Could these 2 issues be related? Anyone have any ideas? Thanks....truck still runs and drives well..knock on wood.

:banghead:

If it is a vacuum leak noise yes.
But under dash is strange.
See if you can pinpoint the source of noise.
And.
Get a repair flow chart for the code 452 and go threw it.
MT

When you hear the noise wit the engine off, pull the hose off the Vaccuum ball under the hood and see if it goes away.
Vacuum leak in the dash could be the defrost/vent/heat selector switch or the hose leading to it.
.

Just to let you guys know. The ringing was still faintly there the next morning after the truck sat all night with the battery unhooked. It eventually went away totally after 2 days. I talked to a friend that works at the dealer here and he said that the factory alarm has a battery backup that is located under the dash and that it was probably that??? He figured something must have set it off somehow. Very weird. Anyhow, the ringing is gone and now I just have my PO452 code to deal with. And of course the tempermental 4x4 issue. It's a love hate relationship with these trucks.

I have the same problem with the PO452 code. Have you figured out what the problem was yet? I am completley lost on this one. My light goes out when I fuel up and comes on when the fuel gets low. Does yours do the same?

Read this post
http://www.automotiveforums.com/vbulletin/showthread.php?t=929172
Your code is for pressure sensor low just the opsite of a code P0453.
But the same repair procedure is required.

what is the repair procedure?....I am so lost on this? My gas cap handle broke off from the part that actually screws out. And the check engine light will go off after I fill up and try to attach the gas cap back together. It's when you unscrew it that it splits apart. When my fuel gets low the light comes back on. When I open the gas cap it sounds like a lot of fuel pressure is coming out like opening a bottle of pepsi. Any suggestions?

As stated in the other post you need a engine capable scanner and a good repair manual with the repair flow chart for that code to do the repair.
Get the repair flow chart from a good repair mauual and go threw it.
This link here has the repair info on it.

http://www.alldata.com/products/diy/index.html

You need to fix the gas cap first.

And best to start your own New thread and give all info.
Year make and model and engine and mileage all code no.