Codes 171 and 174 deal with a lean air fuel mixture. 171 = lean bank 1 / 174 = lean bank 2. Just remember that a lean condition will occur when air gets into the intake that the PCM does not know about. This can happen when the MAF does not report accurate information or there are vacuum leaks or even the O2 sensors are reporting incorrect information. A lean condition can also be the result of low fuel pressure. Have you performed all of the regular maintenance items first? (Ie fuel filter). Also, have you checked fuel pressure?
The 302 and 304 deal with a ignition misfire. This is most likely as a result of the other problem.
I can't say that a tune up will fix this. I do recommend checking fuel pressure and carefully check for vacuum line leaks.
Let me know what you find.
Friday, January 23rd, 2009 AT 5:53 PM