Thread: PO171 Code
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Old 12-17-2009, 09:28 AM   #3
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Join Date: Mar 2000
Location: Memphis, TN
Posts: 5,007

2008 Astra XR
Default Re: PO171 Code

I have some experience with that code...

I got a check engine light, OnStar said it was the fuel cap, so I took it in for the cap/filler neck replacement. While it was there the dealer said it had other codes for a bad O2 sensor. Replaced the sensor (and the manifold assembly because it was stuck). The light came back on, this time it was for running lean. Dealer said they couldn't find anything wrong and reset the computer (thinking that it needed to relearn the new O2 sensor). Light came back on (don't know what code this time), and they ended up replacing the fuel pump after it failed a pressure test.

I never really noticed it running poorly, but I *think* it runs better now. But here is one sign that I didn't think much of at the time: The BC for about a year showed about 2mpg less than what I'd calculate from the pump. When I got the car, it showed about 0.5mpg more. In my case the fuel pump wasn't sending enough fuel causing it to run lean, and it confused the BC since it doesn't actually measure the volume of fuel used directly.

As you can see from the above post, there are a number of things that can cause a P0171. In my case it ended up being a bad fuel pump.
Past Saturns: 97 SL2, 01 SC2, 04 VUE, 08 Astra, 02 L200.
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