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Matt Kesler
Matt Kesler, ASE Certified Mechanic
Category: Chevy
Satisfied Customers: 2734
Experience:  ASE Certified - 20+ Years of Experience
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What does the engine code P0496 mean

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I have a Chevy Trailblazer and I get the code P0496 from time to time. I have had it read and cleared several times and after a week or so it comes back.
Code P0496 is defined as "Evaporative Emission (EVAP) System Flow During Non-Purge"

If the Evap purge valve does not seal properly, fuel vapors could enter the engine at an undesired timing causing drivability concerns. The control module tests for this by commanding the EVAP purge valve OFF closed and vent valve ON closed, sealing the system, and monitoring the FTP for an increase in vacuum. If the control module detects that Evap system vacuum increases above a calibrated value, DTC P0496 will be set.

This could be a sign that your purge valve is intermittently failing so you might want to get it checked out before it turns into a bigger problem that affects the drivability of your truck.
Customer: replied 10 years ago.
How do I check the Evap purge, and where do I find it?
The first step would be to simply clean the valve and see if that helps. The purge valve will be an inexpensive part (probably $20.00 or so) so I'd usually just replace it instead of trying to test it to thoroughly. I've found it can be a somewhat tough part to come by a third party dealers (Napa, Autozone, etc.) So you might have to contact your local Chevrolet dealership parts department to buy the part.

The best thing to do would be to ask the person at the repair dept who sells you the part to copy the page with the replacement guidelines from the service manual. You usually won't have any trouble getting them to do this and then you'll have a good written copy to follow while you change the valve.

The other option would be to have a local mechanic do the replacement for you. On a Trailblazer I'd estimate you'd just be looking at $20.00 for the part and 45 minutes labor (my labor charge is $50 an hour) so that would be a total of $55.00 at my shop. Might be inexpensive enough that it would be worth your time just to bring it in.
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