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Trouble code P0174

This is a discussion on Trouble code P0174 within the General Help forums, part of the LSx Technical Help Section category; Fuel trim system lean bank 2. But what does that mean? What do I look for?...

  1. #1
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    Trouble code P0174

    Fuel trim system lean bank 2. But what does that mean? What do I look for?

  2. #2
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    Red
    2002 T/A

    Which car abd which engine?

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    98 Z-28 Ls1

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    Red
    2002 T/A

    Bank 2 is the passenger side of the engine, Cyl. 2,4,6, and 8. This code is set because the PCM "sees" too much oxygen for the amount of fuel on that side of the engine. A couple of things may cause this. I will list the more common failures. First, you need to understand that the o2 sensor reports this info to the PCM. Here we go. If you truly have a lean condition it may be caused by a partially plugged/dirty injector or two on that side. If you have a "false" lean condition this may be due to an exhaust leak on the passenger side exhaust manifold, AIR pipe, or EGR pipe. The exhaust leak may allow outside o2 into the exhaust stream. This free oxygen is picked up by the o2 sensor and reported back to the PCM. Some misfires will also trick the PCM into a false lean condition. Since the air/fuel mixture is not burned it makes its way into the exhaust stream. Remember the o2 sensor cannot "see" raw fuel it can only sense the oxygen. Misfires generally set misfire codes like P03xx, but not always. Tiny vacuum leaks near the intake ports on the passenger side of the intake manifold or injector o-rings. These vacuum leaks, however, generally produce misfires, but not always. Finally, we get to the o2 sensor itself. If the o2 sensor is lazy or biased rich(broken) it could send an incorrect signal to the PCM as well. Good luck.
    P.S. AIR=Air Injection Reactor
    EGR=Exhaust Gas Recirculation
    PCM=Powertrain Control Module (car's computer)

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    Thanks for the info and the quick response.

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