Does anyone know what to do to fix this problem of the Vent Valve/Solenoid Circuit code? Does anyone know where to find the EVAP Vent Solenoid Control circuit on the vehicle? This is the only code popping up. We had a lot of trouble getting it inspected last year due to the EVAP monitor not closing and it finally did. But now this code wont let it close again.

 

I had this code nagging me and finally hit the forum to get some guidance. A search for P0449 on the forum provided some good info that allowed me to locate and fix my vent valve solenoid which was stuck closed (couldn't blow through it).
Location (1998, 4dr 4wd) (pic evap solenoid):
Above spare on rear of cross member. Has a ~3/4 inch hose and electrical connector.
Tools:
13mm socket/wrench
channel locks
two test leads with alligator clips
pick or small flat blade screwdriver
Procedure:
Drop Spare (while your there - wd40 the cable and insert the wd40 straw into the cable guide and give that a good dose)
Remove vent valve bracket (13mm)
Remove electrical connector (standard lock type can be done by hand)
Remove hose from valve assembly (channel locks)
At workbench - gently remove top of box (4 tabs) and remove mesh filter
Gently pry up lock tab on top of solenoid (pic sol clip) and twist 1/4 turn to remove solenoid valve from vent box
Clean box of any debris - rinse with hot water and dry thoroughly
Attempt to blow through the valve. With no power to the solenoid, you should be able to blow through it. (0 volts = open, 12 volts = closed)
Gently see if solenoid is stuck by inserting pick or small screwdriver in middle port and moving valve seat (pic sol seat). Be careful to not damage the valve seat. Lightly WD40 the solenoid stem.
Connect solenoid to 12 VDC to check the solenoid. I used jumpers to my battery. Connect the ground jumper to one pin in the solenoid. Touch the remaining pin to a jumper connected to the positive battery terminal (caution - don't let your Pos jumper get away from you). With 12 VDC applied, you should hear the solenoid activate and you should not be able to blow through the valve. You can also watch the valve activate under power from the middle port (the hose connection).
Once you are satisfied the valve is functioning or have replaced it, you may need to clear your code or operate for a number of cycles to allow the code to clear. Hope this helps.