Could P0449 on 08 Impala be linked to P0556 vacuum leak?

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May 1, 2025 at 5:53 pm #85 Reply
Nathan
This is new. Any idea? 08 Impala 3.9.

Bad purge valve? I’ve replaced it with a dorman one about a year or so ago. I’ve also replaced the FTP sensor, fuel cap and the Evan canister before also.

I do also have a P0556 code for a brake booster vacuum leak I haven’t been able to track yet. Could they be relate?
May 1, 2025 at 5:56 pm #88 Reply
Michael
It might if the brake booster is allowing a large vacuum loss, almost never is a fuel cap bad, however auto counter will sell you a cap that is what they do, sales, they are not mechanics they are sales counter workers, simple sales jobs.
May 1, 2025 at 5:58 pm #89 Reply
Brian
You can remove the purge valve and try to blow through it. If you can pass air through it either way, it’s bad. Dorman parts are trash. Buy an OE and be done. The p0556 could be related but most likely not.

Conditions for p0556 is engine at idle w/ brake booster vacuum less than manifold vacuum for 100ms or more. If the purge is open, it MAY set this code but I’ve personally never seen it.

If you fix your evap issue and p0556 returns, I’d check for vacuum leaks, if there are none, I’d replace the vacuum sensor on the brake booster.
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