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Discussion Starter · #1 ·
Basically, bank 1+2 are running lean.
From what I understand this typically indicates vacuum leak. (eliminating dirty injectors: I use seafoam regularly through fuel and manifold)
However, recently I had to take out the oxygen sensors because I was painting the heat shield.
I know that most people misdiagnose the code as problem with the oxygen sensor, but how can I be sure that it isn't the oxygen sensor?

Just to get a bit more specific, there is no symptom. The engine runs perfectly.
I have tried disconnecting the battery, and the code goes away for about 10-20 miles, then comes back.

Any feedback will be appreciated. Thanks.
 

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It's not the oxygen sensors, because:
- you don't get any oxygen-sensor codes
- both banks are running lean simultaniously.

which also would indicate that you don't have a leak in the header itself, if you had a leak you would get a P0171 or a P0174, depending on what side the leak was on. Same theory rules out the injectors, a faulty injector would result in either code, again depending on the side.

So the problem should originate in components before the engine:
- vacuumleak in intake-trajectory
- dirty maf

I had these two exact codes a while ago. A clamp of the intake-tube was loose and my maf was dirty.

Check those two things first. Succes !
 

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^^^ +!..

He has it nailed..

The Only thing I'd add is.. Do you have an Aftermarkett Intake.. they will cause problems..

Cap
 

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Discussion Starter · #4 ·
I found that MAF was quite dirty, so I cleaned it with MAF cleaner.
While at it, I thought dirty MAF may highly suggest dirty throttle, so I bought the throttle cleaner as well.
To my surprise, the throttle looked as if it just came out of the factory.

I can't know for sure if that fixed the codes yet. Will find out on my way to work tomorrow.
 

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I know this is old, but...
I had the P0171/4 codes, freeze frame said it was happening about 72 MPH, with about 33% throttle.
I added injector cleanter and it went away.
Hope this might help somebody
 
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