i keep gettin this check engine light and the p0174 code. i cleaned the MAFthen iput in a new o2 sensor. i replaced the front o2 because that sensorwould lean out the fuel/air ratio correct? should i have replaced the back one? also, i dont hear any vaccum leaks

 

bump

 

Your right about the front sensors helping calculate the A/F ratio. It also is calculated by the MAF and TPS as well. Another guess would be that maybe you have low fuel pressure, or maybe bad injectors. Just a guess.

 

yep thats happened to me and i thought it was my O2 sensor also but it ended up being a hole in the fuel line (between the fuel rails) being burned by the EGR pipe.