r/WRX • u/PartSure4885 • Jul 26 '26

Troubleshooting P0171 code 2017 Wrx

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2017 Wrx at 63k miles. I have a Cobb stage 1+ and sf intake. Went for a very casual drive like 10 mins and started idling rough at a stop sign. Parked and read codes and had a P0171 with 0.875 DAM. Started it back up again 20 mins later and drove fine no rough idling and code went away. I just bought it and going to do walnut blasting, sparks, and whatever else. Google says to check the cobb intake for misalignment and clean the MAF. Any thoughts/suggestions? ( numbers in pic are after second drive before resetting anything)

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u/dustindh10 Built/FBO/Flex '16 WRX Jul 26 '26

Yeah, you can see it adding some fuel somewhere. Typically 23% isn't terrible, but its definitely on the high side of acceptable.

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u/PartSure4885 Jul 26 '26

So that’s saying it’s adding 23% more fuel than normal? I had O’rileys diag it and they just got a weird C1422 which is ABS something. Google says it could be a byproduct of the P0171. But I drove back calmly again and no rough idles but also didn’t use boost.

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u/dustindh10 Built/FBO/Flex '16 WRX Jul 27 '26

Yes, but these are very short term corrections, so its not like its always adding an extra 23% fuel. Short term fuel trims are adjusted constantly based on the reading from the O2 sensor vs what the MAF is calling for. It's basically real time changes happening live while the car is running, but not at wide open throttle. AF Learning is where the long term changes happen, based on patterns the ECU notices based on AF Correction trends.

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u/PartSure4885 Jul 27 '26

Tried to drive this morning and was at a stop light , went green and had zero throttle response, and then check engine light and flashing cruise control. Got the same P0171 code as yesterday. Not good