P0174 means the o2 sensor is telling the computer that it's reading a lean-fuel condition in "Bank-2" of the exhaust system. Because you say your exhaust was loud, that sounds like you have an exhaust leak that's allowing air into the system up-stream of the sensor. This could be from a cracked exhaust manifold/pipe//converter, or a bolt has come loose.
It shouldn't be too hard to locate the leak. Good luck, and if you need help making a fix when you do, feel free to write back.
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Friday, June 14th, 2013 AT 2:42 PM