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Code Battle p1491


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I understand this most likely an emissions code, Vacuum bypass seal perhaps? Any common issues and can someone please help break down the location of possible issued areas? I am very confused about how vaccummes and hoses function. Anythings helps!




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It's a code for a vacuum bypass valve.

Which opens up at certain conditions to check the integrity of the evap system.

Vacuum supply hoses should be inspected for cracks/leaks, repair if found.


Check connections, power to the connector should not exist with engine off. It may toggle on/off when ignition is turned on.

Remove valve and blow through it. If you can blow through it, replace it. Valve is stuck open. If unable to blow through it, bench test it with a battery. Should click when energized, and you should be able to blow through it. Replace if it doesn't open.

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