If anyone has their HHR come up with a P0449 code don't take it to the dealer to fix.
It is a quick and easy fix, only cost me $30 in parts and my time.
Dealer wanted to charge me $180 to do the job. Said that GM changed the plus style on solenoid and I had to buy a jumper wire as well as solenoid.
Went to my local PepBoys, bought a replacement solenoid, and an Innova Equus 3030 diagnostic tool so I could erase code. Bonus is I can use the diagnostic tool on almost all cars 1996 and newer. Solenoid is made by BWD (part #CPV43), not an ACDelco but still made in the USA. It has the new GM style plug, but it comes with the jumper wire included.
1) back your HHR up onto a set of ramps - this makes it easier to get to the solenoid.
2) disconnect the wire plug from the solenoid (it is on the back side).
3) gently push retaining clip back and slid solenoid off of charcoal canister.
4) push in on both retaining clips on vent hose and slid it off of solenoid.
5) take rubber seal off of old solenoid and place it on new solenoid.
6) gently slid new solenoid back onto charcoal canister until retaining clip clicks.
7) slid vent hose back onto solenoid until retaining clips click.
8) gently tug on solenoid and vent hose to make sure everything is secure.
9) connect new plug to solenoid and clip old style end to rear cross member.
10) connect old plug to wire jumper.
11) connect diagnostic tool to vehicle, clear code, and remove diagnostic tool.
12) start vehicle, verify engine light does not come back on, and drive it off ramps.
Picture below is with new solenoid installed. You can see the "red" jumper wire connection attached to cross member.