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2004 hummer h2 6.0 codes p0171, p0174, p0300, p0420. This…

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2004 hummer h2 6.0 codes...
2004 hummer h2 6.0 codes p0171, p0174, p0300, p0420. This vehicle also has a after market cold air intake, mass air flow sensor and shorty headers with factory cats and y-pipe, common causes for these codes and where to start?
Submitted: 6 months ago.Category: GM
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Answered in 3 minutes by:
12/29/2017
GM Mechanic: kalamykid, Shop Owner/ Tech replied 6 months ago
kalamykid
kalamykid, Shop Owner/ Tech
Category: GM
Satisfied Customers: 5,515
Experience: I HAVE OWNED MY OWN SHOP FOR OVER THREE YEARS. I HAVE THE TOOLS AND SOFTWARE TO ANSWERE ALMOST ANY Q
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When I see all of these codes, there are two possible problems. There is a vacuum leak or the mass air flow is dirty or going bad. The first thing I would do would be to check for broken vacuum lines, or a hole in the air intake system past the mass air flow and clean the mass air flow with a good cleaner made for mass air flow sensors.

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