Here is a tip I found on my online repair info give it a try and let me know it would explain both codes let me know what you find?
5.3L Check engine light on, code P0449 vent sol. Circuit.
Found vent solenoid rotten, it sits kinda on top of spare towards front of truck, you can see a small amount of rust coming through the body of the actual solenoid on the vent.
Wish I had one of dem dars picture cameras to show you.
Have replaced quite a few of these on these trucks
Tuesday, December 4th, 2012 AT 11:26 PM