P0171 Code
Thread Starter
8th Gear
Joined: Mar 2012
Posts: 8
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P0171 Code
I have an 06, only mods are CAI and axle back exhaust. No tune that I know of. Car has 38000 miles. No idea of maintenance history other than oil changes I did.
Not every time, but almost every other time I start it, CEL and P0171 code. Before I do something stupid and load the parts cannon, what should I check first?
Thanks in advance.
Not every time, but almost every other time I start it, CEL and P0171 code. Before I do something stupid and load the parts cannon, what should I check first?
Thanks in advance.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,320
Likes: 3,927
From: Cape Coral, Florida
Depending on what your fuel trims are you are either turning left or right...if one banks (left bank) fuel trim is elevated could be an intake runner vacuum leak or if bank 2 is elevated but has not increased high enough to set a P0174 you will go down another path such as an intake leak or possible fuel delivery or MAF issue...if long terms are both elevated run the engine at 3000 RPM for a few minutes...if they start to decrease you have a vacuum leak...if fuel trims are near 0% at idle but INCREASE under load can be a fuel delivery or a MAF issue…normally a dirty MAF will have fuel trims negative at idle but go positive under engine load…looking at “freeze frame” data with the scan tool will tell you what RPM the P0171 code set at…if idle equals vacuum leak…if at cruise fuel or MAF.
Last edited by C5 Diag; Jan 7, 2025 at 04:03 PM.
