Your check engine light has been active for the past several weeks. Although you haven't noticed any significant performance issue, you have experienced a rough idle. As any auto-savvy driver would do, you hooked up your OBD scanner to your vehicle and discovered a P0441, P0443, or P0445 code—a purge flow fault in your evaporate control system. In most cases, this problem is repaired by replacing your purge valve. Here's how to test and replace it yourself:
Confirm Faulty Purge Flow
Unfortunately, there are other components in your EVAP system that can trigger your OBD codes. For this reason, you'll need to inspect a few components of your system before you replace your valve. Otherwise, you may replace your purge valve only to discover it wasn't the cause of your problem.
Raise your vehicle with a hydraulic jack and jack stands. Inspect the series of EVAP lines leading out from your engine compartment. Follow the lines back towards your gas tank and charcoal canister and inspect them for any signs of damage. After following the lines beneath your tank, open your hood and follow the lines to your purge valve. If your lines are still in good condition, then your purge valve may still be the culprit responsible for your engine light.
However, if your lines are even slightly damaged, then have them professionally replaced. Unless your purge valve is malfunctioning as well, fixing your lines will turn off your check engine light.
Use A Vacuum Gauge
Once you've confirmed that your EVAP lines are still in good condition, you must test your valve with a vacuum gauge. Your purge valve will be connected to your throttle body. Follow the hose leading beneath your throttle body until you encounter your purge valve. Disconnect the electrical wiring clip from your valve. Use a pair of pliers to remove the clamp that connects your purge valve to the line leading towards your fuel tank.
Connect a vacuum gauge to the disconnected end of your purge valve and start your vehicle. If the gauge rises even slightly, then you have just confirmed that your purge valve is responsible for your check engine light. However, if your gauge didn't detect a vacuum, then double check your gauge's connection and try again. If the gauge still doesn't rise, then your valve isn't the cause of your engine light.
Replace The Valve
After you've confirmed that your purge valve is faulty, reassemble your purge valve and head to your local auto parts store for a replacement.
Once again, disconnect the electrical clip on your valve and remove the clamp from the line leading towards your fuel tank. Next, remove the mounting bolt or screw that secures your valve to your engine. At this point, your valve should be hanging only by the clamp and line leading into your throttle body. If your valve is still secure, then check your vehicle's service manual to determine which other mounting components must be removed.
With all mounting fasteners removed, you can remove your valve by using your pliers to remove the last remaining clamp and line connected to your valve. Pay attention to the orientation of your valve while removing it—you must install your new valve in the same orientation in order for it to operate correctly.
Take your replacement valve and, while maintaining the correct orientation, slide the upper end of the valve into the hose leading out of your throttle body. Slide the clamp over the end of your valve and reinstall all necessary mounting fasteners. Take the line from your gas tank and slide it onto the lower end of your valve. Use your pliers once again to secure the clamp on the line and complete your EVAP system's vacuum. After securing your new valve, reconnect your electrical wiring.
Test Your Work
Reset your check engine codes with your OBD scanner and restart your vehicle. If you installed your valve correctly, then your rough idle and check engine light will no longer be present. If these problems persist after replacing your valve, then there's a more complicated problem with your EVAP system that requires professional attention at a local auto repair shop.