So I ended up picking up an 03 Silverado Z71 for winter as I didn't want to drive my brand new LML Duramax in the wonderful snow and salt up here in PA. After looking over the truck before I bought, everything looked and ran good. 128k on the clock on the 5.3 still runs real strong. On the way home, the check engine light came on I was hoping it was nothing serious, because I got a really good deal on the truck. All I could think is here is why I got it so cheap. So I roll into the local AutoZone and have them scan the code. Comes up as P0449.

"The PCM has determined that a malfunction exists in the electrical circuit for the vent valve/solenoid in the evaporative emission control system.

EVAP (Evaporative Emission System) purge/vent solenoid circuit condition

The solenoids and system wiring are monitored for opens or shorts

Probable Causes
1- Purge or vent solenoids defective
2- Check connector and wiring
3- Fuel saturated vapor canister
4- Failed EVAP vent solenoid"

Sounded pretty scary and AutoZone didn't carry the replacement part, said it was a "dealer only" part. So they cleared the code for me and off I went. On the way back to the house, the light came on again. After doing a quick Google search when I got home, I found that this is a very common problem on these trucks. However, all of the information that I found was very confusing and so many people have been trying so many different part numbers. I figured I would write this up to help all of those who have this problem or may run into it during their ownership of one of these vehicles. Its a very easy fix and considerably cheaper doing it yourself than taking it to a garage or even worse, the dealer. In total it cost me $22 to fix (compare this to many dealers $100 diagnostic fee alone just to tell you whats wrong!) Hope this helps anyone who needs it

The Victim:

The Concern:

The Culprit:

The EVAP purge/vent valve was located on my 2003 Z71 ext cab short bed between the bed and rear of the cab on the drivers side. Outside of the frame rail between the frame and outer bed fender. To remove the malfunctioning part, all I had to do was loosen the hose clamps and pull the hoses off the valve and disconnect the electric plug. The valve itself slides off of the metal bracket that is attached too. I dont know if this part was original to the truck or not, but the hoses were a real pain to get off. Even with the clamps totally loosened and pulled back, the rubber had a really good grip on the valves plastic. Getting one hose off, allowed me to work the valve side to side while pulling and made it a little easier to remove the hose.

The Replacement Part:

I was able to find an AC Delco replacement part (AC Delco Part # 214-2149), cross referenced with the GM part number I found online. AutoZone in my area doesn't sell these, I got it from the local Advance Auto Parts for $22. They list the part as an "EGR Solenoid" but it is the correct purge/vent valve solenoid needed for this job. The install was literally as easy as plugging everything back in and reattaching the new part back on sliding it on the bracket as the old part had come off.

The end result:

Trucks running great and no more check engine light 100 miles later and multiple restarts. All codes have been cleared just by letting the system sense the new part installed. You could force the code to clear by resetting the computer if you have a scan tool or disconnecting the battery for 15 minutes. But I just drove mine and by the 3rd cold start up the code had cleared itself.

I hope this helps anyone who has this code or has tried other things to fix it. The most common response to this code is that the "gas cap is loose". If the gas cap isnt loose or has already been replaced, then this is probably 99% going to be your problem. Good luck guys!