That code just mean the o2 sensor 1/1 reads a lean exhaust. A low fuel presure will
also set code p0174 for 2/1 sensor. Many things can cause this code to set. There is
no one answer to this issue. You must follow the diagnosis procedure shown in your
shop repair manual. Ondemand5,alldata. Possible causes will be o2 sensor,
wiring,pcm,engine mechanical,fuel delivery ,ect sensor or wiring,map sensor or wiring
and or exhaust leak. The first thing I will do is swap sensors if problem changes
places you know is a sensor problem, if not more testing is needed, check all wiring
and connectors, make sure there is no exhaust leak before the sensor, good luck.