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service eng soon code

Discussion in 'E46 (1999-2006)' started by 330apple, Mar 18, 2011.

    330apple guest

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    Does anybody know what a code of P0174 (system too lean) is asking for--------is this a reprogram computer fix---------in the old days I just opened the main jet a little!!! Help/ Apple oh this is a '05 330Ci
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    Specifically, I don't; obviously sounds like it's ("the" system, whatever system "it" is) getting/detecting a lean-running-condition, and triggering an alert. Perhaps possible it's just a one-time trigger or glitch that perhaps a reset would resolve, but if not, then you're into fuel-system diagnostics. Stuff like fuel pumps, filters, lines, injectors, not sure if your model has a pressure regulator or not... stuff along those lines, though.
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    It does and it's integrated with the fuel filter.
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    Try cleaning your Mass Air Flow Sensor (MAF) first. If it has the least bit of grime it can misread the temperature of the air flow into your engine. This little devise sends the signal to the computer that controls the mixture and it's all based on based on this temp. If it's dirty it could be directing an extra lean mix. It's very easy and inexpensive. CRC sells spray MAF cleaner - it's very similar to electronic connection cleaner and you can find it at all the auto parts stores - just go to the air cleaner, follow the tube toward the engine, undo the clamp(s) and carefully separate the MAF from the rest and look for the little platinum coated leads down the inside of the MAF. Give them a couple shots of cleaner and you're done. Do not under any circumstance touch these sensors with anything other than the stream of cleaner. They break easily and a new MAF will run you $hundreds. Just let the cleaner evaporate (keep it away from flame, it is extremely flammable) and then reattach the MAF to the air cleaner and see if your light goes out. If you are lucky (like me) that may be the end of it, if not, well now at least you have a clean MAF. Good luck!
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    • Technical Service Advisor


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    Most common cause of a lean condition in your model is a torn intake boot. You will want to have it checked out.
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    west76 guest

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    yep, the boots on the e46 are notorious for rotting out and throwing codes. when you check them, don't just do a visual inspection. feel / press each boot with your hand to look for cracks. they are pretty easy to replace too if that's the problem
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    Probably MAF

    I had the same code before at around 90k miles right after changing the air filter to those "lifetime" performance part. The mechanic said he wouldn't advise cleaning and replaced with new which was in the $300s.

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