P0449 - Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction
Unfortunately, like many fault codes, this isn't real descriptive. There are entire books published just for diagnosing these codes. I can think of two common things that could be involved. The most likely is a problem with that valve's solenoid, which is a coil of wire, or the wiring and connector terminals associated with it. That circuit is real easy for the Engine Computer to monitor and set a code for when appropriate.
The second potential cause is when the computer opens that valve to draw fuel vapors out of the charcoal canister, it expects to see the results of that extra fuel show up as a momentary rich condition in the exhaust. It may be not seeing that change occur, possibly due to a pinched hose or a sticking valve. An engine performance specialist will look at the oxygen sensor readings on a scanner, and watch how they react when introducing artificial lean and rich conditions. He can use the scanner too to actuate that solenoid and listen if it's working. That will tell him if it's an electrical problem or a mechanical problem.
Sep 15, 2015 at 1:50 PM
