ToughFX4

p0171 fuel trim bank one condition

aa1 if bank one and two codes set together suspect fuel pressure or mass air sensor

aa2oxygen sensor defective

aa3ignition misfire-repair

aa4fuel injector problem

Keep in mind my truck runs good no problems,just the check engine light on with code p0171.

bcingle

I know it's a month and a half later, but I'm having he same issue. It started with a couple bad COPs, but those are fixed and I still get P0171. Did you ever come to resolution on this? Most of my research suggests an airflow leak somewhere on the passenger side, since it's not throwing P0174 along with it. Thanks.

g8rfan

I sure was hoping to see some follow-up to this post. My CEL in my 2004 FX4 5.4 came on Friday and the only code it threw was P0171. Did you guys ever fix your issue? If so, what was it?

s_vares

if there is no misfire, try checking the 1st (primary) O2 sensor

clarsen

Can a miss cause this code to come up? I have new coils on way and a known miss on cyl 6.
Note all new Bosch o2's about a year ago.

Mod (Ret.)

Any time you have a situation where a cylinder was not firing, this can cause raw fuel onto an O2 sensor, and "corrupt" it. Once the original issue is resolved, the O2 sensor would need to now be replaced.