Codes 171 and 174 03 ranger.
 

Only pulles these codes after idling more than 3 min. Replaced pcv and line to it. Wat else could it b?
Fixed one problem. Now thows 171,174 and 534. Got lean codes figured out. But wat is causing 534?

Welcome to the forum

Hard to memorize all the OBD codes so best to post what each means since you probably looked them up.

P0171 = system shows Lean on Bank 1(passenger side of V engine)
P0174 = system shows Lean on Bank 2(drivers side of V engine)

If both sides of a V6 engine show Lean code then it won't be an O2 sensor problem since each side has its own O2 sensor, and both O2s would have to fail at the same time, a long shot

Lean code doesn't mean engine is actually running Lean, it means that the computer's calculated air/fuel mix is Lean after feedback from O2 sensors, so computer is adding more fuel than it "thinks it should" based on air flow data from MAF(mass air flow) sensor.
So engine is not being hurt by Lean codes and it is OK to drive

If there is a Vacuum Leak, then all the air coming into the engine is not flowing thru the MAF sensor, so computer's calculation would be off, there is more air so it would be a Lean fuel mix.
You changed the PCV Valve and hose which could have been the source of a vacuum leak, but wasn't if it didn't fix the problem.

Simple test for a vacuum leak is to warm up the engine.
On the upper intake is the IAC(idle air control) Valve, it has 2 wires connected
With engine warmed up and idling, unplug these 2 wires from IAC Valve
idle should drop to 500RPMs or engine may even stall, either is GOOD, it means no vacuum leaks
If idle stays at 700 or higher then you have a vacuum leak
leave IAC Valve unplugged and try to find a leaking hose, any hose connect to upper intake.

If no vacuum leak then Clean the MAF sensor, easy to do.
Also check the large air tube from MAF sensor to the intake manifold, if it is cracked or broken then extra air will come in and through off computer's calculation

If MAF is clean and no vacuum/air leaks then could be a Fuel Pressure problem.
2003 Ranger computer expect fuel injectors to have 60-70psi fuel pressure pushing fuel into intake.
If fuel pump is only able to do 20-40psi then calculation will be off, Lean mix, so computer has to open fuel injectors longer because of lower pressure.
Computer doesn't have a fuel pressure sensor

Am also dealing with same codes (+2months). No intend to hijack this thread but I have question.
2000 ranger 3.0L flex engine (new remanufactured)
Have smoke test, replaced MAF, o2 sensors, IAC, EGR, ... mechanic went step by step thru recommendations.
Pressure test at shrader valve reads 54psi. a call to Ford service tell me to expect 55
+/-8 psi
quoting RonD " 1998 was first year of Returnless fuel system on Rangers, they run at 65psi pressure, damper prevents pressure waves from building up in the rail"
does this mean that my 54psi is the cause of p0171 p0174 codes ?

[QUOTE=RonD;2119064]Welcome to the forum

Hard to memorize all the OBD codes so best to post what each means since you probably looked them up.

P0171 = system shows Lean on Bank 1(passenger side of V engine)
P0174 = system shows Lean on Bank 2(drivers side of V engine)

If both sides of a V6 engine show Lean code then it won't be an O2 sensor problem since each side has its own O2 sensor, and both O2s would have to fail at the same time, a long shot

Lean code doesn't mean engine is actually running Lean, it means that the computer's calculated air/fuel mix is Lean after feedback from O2 sensors, so computer is adding more fuel than it "thinks it should" based on air flow data from MAF(mass air flow) sensor.
So engine is not being hurt by Lean codes and it is OK to drive

If there is a Vacuum Leak, then all the air coming into the engine is not flowing thru the MAF sensor, so computer's calculation would be off, there is more air so it would be a Lean fuel mix.
You changed the PCV Valve and hose which could have been the source of a vacuum leak, but wasn't if it didn't fix the problem.

Simple test for a vacuum leak is to warm up the engine.
On the upper intake is the IAC(idle air control) Valve, it has 2 wires connected
With engine warmed up and idling, unplug these 2 wires from IAC Valve
idle should drop to 500RPMs or engine may even stall, either is GOOD, it means no vacuum leaks
If idle stays at 700 or higher then you have a vacuum leak
leave IAC Valve unplugged and try to find a leaking hose, any hose connect to upper intake.

If no vacuum leak then Clean the MAF sensor, easy to do.
Also check the large air tube from MAF sensor to the intake manifold, if it is cracked or broken then extra air will come in and through off computer's calculation

If MAF is clean and no vacuum/air leaks then could be a Fuel Pressure problem.
2003 Ranger computer expect fuel injectors to have 60-70psi fuel pressure pushing fuel into intake.
If fuel pump is only able to do 20-40psi then calculation will be off, Lean mix, so computer has to open fuel injectors longer because of lower pressure.
Computer

54psi is fine, under 40psi is when it starts causing issues

Codes 171 174
 

Took a long drive (400 miles round trip) on Ranger.
Hookup a scanner + monitor RPM, STFT1, LTFT1, STFT2, LTFT2

Short term fuel trim 1 & 2 are swinging about 2- 35%
Long term fuel trim 1 & 2 are hanging about 25%, seemed rich,
but no codes are triggered while driving. No pending code before shutting off engine.
P0171 P0174 are registered within 2 minutes after restarting truck....

On way back, stopped and bought laser thermometer, measured temp at input/output of 2x catalytic converters, both side read about 600F

Hook up scanner to monitor the 3x o2 sensors:
the 2 pre cat sensors swing correctly .1v - .8v.
the post cat sensor swing all over from .2v- .6v

these 2 tell signs, + that I just replaced all 3 o2 sensors point to bad cats

Will be shopping for this online, the Ford dealers wants ++$1200

ROND, thank you for the answer about minimum fuel pressure.

Codes 171 d 174
 

Check pvc line that goes to right side valve cover. O-ring may have small crack. I replaced the o-ring and gently tapped it back into place. No more codes so far.

There is a hose going to the valve cover that was loose, I tightened it with a zip tie + it did a little bit of improvement. but still codes.
PCV is new, was thinking that it is loose so I just checked fitness and condition. looks + feel thight.
Called parts store yesterday to order Catalytics + found out that there are 3 of those cats.
front has 2 on the Y pipe, and a rear Cat at the outlet of the Y, so I crawled under to check. Looks like original parts with +++200K miles in it; at the pipe outlet of the rear cat, there is evidence of fresh burned/ gummed up oil residues. don't think they are clogged up, likely worn out.