August 11, 2010
Hey Rob....How have you been? This code has been bothering me for several weeks now. It started out as PO455 which is a Evap Emission Ctrl Sys Gross Leak Detected then one day changed to DTC PO456 which is Evap Emission Ctrl Sys Very Small LeakDetected. All along I kept getting the tighten gas cap error on the message display. So I changed the cap and the error went away for 2 or 3 days then the PO455 error came back again. Right after clearing it a PO449 error showed up (Evap Emission Ctrl Sys Vent Valve/Solenoid CircError). So after talking to a few people on here and a good friend at my local dealship I decided to look into the Vent Valve Solenoid. My friend at the dealership said that there is a recall on the Vent Valve (Unfortunitly it is not an open recall only a voluntary) due to dust clogging up the intake port. He claimed that with my vehicle only have 38,000 miles on it and not being in a real dusty enviroment he couldn`t guarentee that was the problem, because the problem normally showed up on high milage farm vehicles and tripped a PO446 Code. Well low and behold I changed it out with the new updated version and for the last 5 or 6 days I have not received a single DTC error.
The dealer ship quoted me about $350.00 for the part and installation and claimed that the transmission would have had to be lowered to install the item. (Per there Data Bulletin) Well I decided to try it myself. The part cost me $104.00 and took about 1 hour to install (give or take 15 minutes). The old vent valve had one electrical connection, a vapor output port and an intake port right on the solenoid. The new piece still clipped to the original bracket and still had the single electrical connection and single vapor output port, but now they remoted the intake port. On my truck with is a 6` bed and standard cab I needed to purchase 10` of 5/8" fuel line/evap hose (GM says to use 5/8 heater hose because it is more readly available however it is that redish brown in color, the evap hose is black) I found it at my lcal NAPA store. With your truck I would guess you`ll need about 16` to 18` of hose. The hose was ran along the inner frame rail and over the top of the tranny to just infront of the "T" fitting that is located on the transmission vent hose. At that point you nylon zip tie this vent valve vent hose to the trans vent hose and add the supplied filter adapter to the end of the hose. That was it....I never need to drop the transmission because I was able to see and get both arms right up on top without a problem.
If you are interested in tackeling the job yourself I can scan and email you the document bulletin that my buddy printed right GM`s parts break down/install dealer site. It basiclly explains everything I just mentioned but also gives you some pictures and other versions of trucks beside my 2007 Classic Silverado.
I hope this info helps you and anyone else that may be having the same issue. Good Luck!