Chevy P0449 – Evaporative System Vent Control Circuit Malfunction
The P0449 engine code pertains to the EVAP system, which is the acronym for the Evaporative Emissions Control System. The purpose of the EVAP system is to absorb fuel vapor from the fuel tank to prevent it from being released into the atmosphere, which is environmentally damaging. The system collects fuel vapors via a canister filled with active charcoal. The captured vapors are then sent to the Chevy’s intake system where they enter the engine and are burned off during the combustion cycle.
Understanding the EVAP System Components
Your Chevy’s gas tank has vent lines which connect to the EVAP canister, which usually sits underneath the car somewhere near the gas tank. Attached to the canister is a vent valve/solenoid which is responsible for letting outside air into the canister to dilute the fuel vapors prior to sending them to the engine.
As the canister fills with vapors, the vapors are then sent out of the canister via purge lines. The purge lines then lead to a purge valve/solenoid which is generally located behind the throttle body. The purge valve/solenoid then opens and closes to release the vapors (and some outside air) into the intake system to be burned during combustion.
Usually, when you have an EVAP failure, it is the fault of the purge valve or vent valve (also called solenoids).
What Happens When EVAP Fails?
Ultimately, when you have a P0449 engine code, it means the vent valve has failed. When the valve fails, it generally fails open. When this happens, the gas vapors are released to the atmosphere instead of sent to the engine. Additionally, the purge valve can get stuck open which can create a vacuum, constantly pulling vapors into the intake system, which can cause some performance issues.
EVAP system failures are also commonly referred to as vacuum leaks.
EVAP Failure Symptoms
- Engine code P0449, P0440, P0441, P0446
- Poor idling
- Out of spec air-to-fuel ratios
- Difficulty starting the engine, in some cases
If you have a small leak, you might not notice any symptoms. While the issue can cause some performance issues from AFR’s, it is usually not serious enough to cause major engine damage. Overall, the easiest way to identify this issue is through the engine code.
How to Fix a P0449 Engine Code – Chevy
When you get a P0449 error code on your Chevy, the problem is most frequently caused by the vent valve failing stuck open. When this happens, you need to replace the whole canister which has the vent valve attached to it. Another possible failure point is the purge solenoid which I’ve included a picture of below. Additionally, this code can be caused by a bad gas cap. If this is the case, you might get a “check gas cap” light on the dash from time to time.
Fortunately, all of these parts are sub $50 and can be DIY’ed relatively easily. If you are going to a repair shop or dealer to have them fix the issue, you can expect to pay somewhere around $200-$250.
Here is a picture of the canister for a 2005 Chevy Tahoe:
Additionally, the problem can relate to the purge valve or solenoid which sits behind the throttle body. Here is a picture of a Chevy purge valve solenoid:
I had that code on my GMC 5.3 after investigating I found that mice filled my exhaust with grain and nests,I cut muffler off and replaced it fixed the problem
My 03 Tahoe has the Po449 and Po300.. I found out that mice got ahold of the injector wires and throttle body wires. I replaced them and started the truck and it runs much better and now have response in the throttle when I rev it. Now the misfire continues and I’m getting a Po449 and its still misfiring. What do you think I should check first?
my truck had code p0449 it was the evap solenoid coming off the canister under the vehicle. There was a crack in it, very common due to water and also cold weather where I live. Fixed the issue and truck runs Great . no misfire or bogging down. Part was 48,00 usually an hr shop time
Thanks for this information. Helpful!
Typically GM EVAP systems have 100,000 mile warranties. Suggest check with your dealer before forking over cash for repairs.
2019 Silverado ,I got code PO 499
I need help thank you
Leobel – per the article check the gas cap. If you don’t have any issue with the cap then you’re going to need to replace the vacuum canister.
no cap tank is capless. I replace the vacuum canister and the purge valve nothing happen
thank you
06 HHR turn key dash lights up but no power. Had key programmer over today but could not program as he was unable to communicate with the brain, he said. Also I get a code Po449. Where to start to get this car going?
Have you looked into the EVAP system as the article suggests? It can cause starting issues but it will typically still crank. Does the engine crank at all? If not, check battery and starter and fuses for each of these. If it does then look into fueling and ignition.