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I have been trying to get the check engine light to go away for awhile now and the codes im getting is p0171 and p0174! and it means "system to lean" So I replaced the fuel filter, cleaned the Mass air flow sensor with a couple sprays of electrical cleaner, ran a couple tanks of that fuel injector cleaner to clean the injectors and replaced bank 1 O2 sensor! I try and erase the codes everytime I do something but they keep coming back..... what should I do next? I heard that if you get those two together its something to do with the MAF or somthing in the fuel? any suggestions is much appreciated.. k thanks!
 

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I have been trying to get the check engine light to go away for awhile now and the codes im getting is p0171 and p0174! and it means "system to lean" So I replaced the fuel filter, cleaned the Mass air flow sensor with a couple sprays of electrical cleaner, ran a couple tanks of that fuel injector cleaner to clean the injectors and replaced bank 1 O2 sensor! I try and erase the codes everytime I do something but they keep coming back..... what should I do next? I heard that if you get those two together its something to do with the MAF or somthing in the fuel? any suggestions is much appreciated.. k thanks!
I would like to know the same thing. I too have both codes plus a P0300.
 

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Those 2 are lean condition codes most of the time we see these it is repaired by replacing the intake gaskets with an updated gasket which is teal in color insted of orange. There's a bulletin addressing this issue. Lean conditions are cause by unmetered air entering the engine, use throttle cleaner on a cold engine to check for leaks, it'll run rough when you find the leak.
 

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spray intake with brake clean watch o2 waveform, spray and goes rich then back to nomal switching then u know its the gasket
 

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I just had this same problem on my V6, codes p0171 & p0174. It turned out to be a universal valve cover breather... the engine saw it as false air not being read by the MAF. And when the short term fuel trim went out of range compensating for the extra air it threw the codes.
 
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