Return Check Engine Light

My check engine light came on, hooked up the obd scan said p0714 & p0171 changed out the fuel filter and both oxygen sensors before the converter. Cleared the codes , drive for a couple of days the check engine light comes back on and the same codes p0171 & p0174 show back up on the scanner. Any ideals on why these are showing back up on the scan.

what kind of vehicle do yo have, what engine, how much mileage, those codes can be caused by numerous things, need a little more info

Jeff

2001 ford explore sport trac 4 wheel drive 148,00 miles v6 4.0 liter. now the only code that comes up is the p0174 code the p0171 code went away. I'm beginning to think that I bought a bad sensor

Which sensor did you replace, an O2 sensor?, those codes are for system too lean bank 1 (po171) and system too lean bank 2 (p0174)
Can be an o2 sensor but the odds that both failled at the same time is pretty slim, more probable cause would be a vaccum leak, intake gasket leak, egr valve failure, low fule pressure, wiring to the heated o2 sensor circuit etc, . If changing a sensor on 1 side removed the code then possible both sensors are just lazy but lots to check before condemming them.

good luck

Jeff

Just got thinking, your codes can also be caused by dirty heating elements in the maf sensor, seems to be a pretty successful repair on both fords and toyota alot, use some electrical contact cleaner and just gently spray the heating elements inside the maf. Might as well clean the throttle body and iac passages while you are in there

good luck

changed both sensors, thanks for your help