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Hello to everyone on here. Im new to Cobalts and am not experienced with any GM vehicle Ive been a Ford guy all my life. I have a 2009 Cobalt that i got last month that is throwing a p0449 code. the guy i got it from said he didnt replace the evap canister solenoid which is what the p0449 code is for. I bought a new one from advance auto and upon removing the "old" one, took notice that the seller had lied and did have a new one installed. I knew right then and there it was going to be a nightmare. I installed the new one, cleared the codes, and right after i cleared it with the engine not running, the code came right back. No matter how many times i cleared it, it would come back immediately even without the engine being started. I started doing some tests, i unhooked the purge solenoid in the engine bay with the key on engine not running and it threw a purge solenoid code immediately. I then hooked both the "old" and new evap canister solenoids to the purge solenoid connection in the engine bay, and the purge solenoid code went away both times so both the "old" and new evap canister solenoids are good. I thought ok, must be a broken wire leading to the evap canister solenoid. i checked over the wiring harness at the rear wheel, and i could not find any cuts or broken wires everything looked pretty good. Afterwards i used a multimeter to see if the purge solenoid and evap canister solenoid was getting power. Purge solenoid in engine bay was getting 8.9 volts with key on engine not running, and to my surprise the evap canister solenoid wiring was receiving 8.7 volts. I dont understand this, if the evap canister solenoid is receiving power, then why is the solenoid not working and a code for it is being thrown? I even tried disconnecting the battery for 30 mins to get rid of the code, but it threw p0449 within about 15 seconds of the key being turned on. My best bud who is a shade tree mechanic as well said he thinks the PCM is shot. Can someone please give me some input on what this could be? It does not make sense to me that the solenoid is receiving power but still will not work. I'm about to pull my hair out...this is driving me crazy i need to get this fixed so i can get the emissions testing done.
 

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P0449 Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction

This doesn't mean you have a bad solenoid. Did you try cleaning the connections at the ECM ( 05-06 PCM )? Maybe corrosion on the fuse block connections, did you pull and re-install each fuse to clean possible corrosion?
 

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Voltage sounds low. 12volt system??????? Hum??????????s Sounds like you might be dropping voltage at a high resistance. I would get my hands on some "deoxit". Guitar Center Stocks it. Check the sources voltage and follow it. Spray the deoxit on the connections it can't hurt and conditions them. Most solenoids need the proper voltage to energize.
 
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