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Discussion Starter #1
Check engine light came on. Did a quick On Star diagnostic test. Codes P0171 and P0174. Anyone else have these issues?
 

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These are the codes for a lean condition on bank 1.
A few common causes are vacuum leak, bad fuel pressure regulator, MAF sensor, O2 sensor.
Do a Google search, tons of info on the net.
 

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I saw some article for the LFX engine and an intake manifold vacuum leak.


if you have a scan tool that can read fuel trims there are some steps in the article that may help figure out the issue. You try to block off some air tube to see if your trims go lower and / or check A purge valve for vacuum leaks. The engine runs lean due to a vacuum leak so the trims go up to add fuel to compensate. Too much compensation and the check engine light comes on.
 

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Discussion Starter #4
Thanks. I did notice i forgot to put the oil cap back on after adding a little oil. Ooops!!. Prolly was left off for a couple days. Nothing super bad. I noticed the check engine light has not come back on after i put the cap back on
 

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Good chance that you just found your vacuum leak.
Keep an eye on it, you should be fine.
 
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