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Mike V.
Mike V., Subaru Technician
Category: Subaru
Satisfied Customers: 25184
Experience:  Certified Subaru Technician, factory trained by Subaru.
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Check engine light is ON. code P0400. The housing which

Customer Question

Check engine light is ON. code P0400. The housing which mounts the EGR valve has grayish water at the bottom. Somewhere I read that this indicates another small valve problem which triggers P0400.What happens next?
Submitted: 1 year ago.
Category: Subaru
Expert:  Mike V. replied 1 year ago.

Hi there,

If you look at the engine you should see a round plastic disk looking item. This is the BPD valve. It regulates some of the vacuum to the egr. If you pull it off and tap it on your hand you might get some water out of the bottom hose. If you do, replace it. This is the most common cause of the 400 code on these.

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