Causes and Fixes Ford P0171 Code: System Too Lean (Bank 1)

How to fix a Ford P0171 engine code: System Too Lean (Bank 1)
A lean condition exists if the engine is getting more air than fuel in the cylinders. (Air/Fuel Ratio is off)
P0171 Code is problematic code since it can be caused by several things.
Ford vehicles with V6 or V8 engines, Bank-1 is on the Passenger side. A 4 Cylinder has only Bank-1.
Possible Causes of a Ford P0171 Code:
Dirty Air Filter
Mass Air Flow Sensor (Codes P0100, P0101, P0102, P0103, P0104)
Clogged Fuel Filter
Fuel Pressure Regulator
Weak Fuel Pump
Vacuum Leak
Oxygen Sensor (Bank 1 Sensor 1)
Bad Fuel Injector
DPFE (Differential Pressure Feedback Sensor) (P0401 code)
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By using this information user assumes all risk of use.

[@jessegutierrez9266]

Thanks bro ....A no bullshit video

[@Conkobonko477]

I have a 03 v6 mustang with this code. I replaced the injectors and I’m waiting on a new fuel pump and filter as we speak. I also have a mean exhaust leak right by bank 1 and that might be the issue ima bring it into a shop to get it fixed soon. but my oil dip stick smelt like fuel so that’s why I did my injectors, but the pump is probably old as hell too. Idk I’m just cleaning up after the people who didn’t do any Maintnance. But now I know i should also check my MAF sensor and make sure it’s working and do a vacuum leak test as well because those could also be giving me issues so thank you!

[@pedrolara1169]

Thanks for your help

[@unosgallosgarcia2668]

your are an A's after working with mechanics and just giving me the run around and taking my money I have decided to take the challenge myself 1996 f150 4.9l engine thank you for your knowledge and sharing

[@sohailahmed3101]

Fantastic sir

[@incognito8386]

I had this code on my 2001 f150. Turned out that the grommets for the IMRC arms had broken and were no longer holding the arms. It was a relatively cheap fix. But a big job.

[@froglobster]

I just got this 171. 08 f150. Cleared code lasted 2 weeks then on again. Was told most popular is 02 sense. Also was suggest that my passenger exhaust manifold leak (common) could be the issue.

[@user-nm5op9nn4d]

I change the oxygen sensors I change the mass air flow sensor change the air filter now I'm about to change the sensor for the injectors

[@AmbA4]

Can also be cause by faulty cts

[@davemiller7633]

What problems lead to a fuel pump replacement?

[@papasmrff2291]

I have a p0171 on my 04 f150 it’s 4wd with the 5.4. What’s odd to me is the vehicle is running beautifully, no drop in rpm no rough idle.. literally. No physical or alarming symptoms. Can anybody tell me if that helps narrow down the possible problems?

[@mark.r8900]

Great tutorial. My 2007 audi a4 giving a p0171. The car starts fine and idles around 1200 rpm then drops to 800 rpm and shakes. I unplugged the brake booster hose and the rpm stays same no change. Shouldn't the rpm rise because I am introducing more unmetered air? I am totally confused. Any help would be greatly appreciated. Thank you

[@HVAC_Mechanic]

This is just a guess, but if there is a big leak somewhere else, there may be no change since there is already a big leak. The MAF sensor may also be having an issue.

[@mark.r8900]

Thank you for your help.

[@Jksnatcher]

Sounds like your brake booster is leaking

[@asidasid2487]

Basically ford expects you to just accept since day 1 of design of all ford's will run either too rich too lean yet in the far past there was no sensors to tell the BS , THAT FORD DOES NOT GOVE TFK

[@PhilphilPhillip-uz4ps]

So basically replace everything until the bad part is found.

[@ricks3313]

My truck threw p0171/p0174 AFTER the Ford dealer replaced my valve cover gaskets. It is driving me nuts. They claimed it's a cracked intake manifold but spraying brake cleaner all around the intake doesn't change the idle at all. Any ideas?

[@HVAC_Mechanic]

If you think there is an intake leak, it may be best to use a smoke machine to check it.

[@mikeleblanc6300]

would the fuel ejector clips be a problem? 3 of them don't click in.

[@user-nn8hb8kr5q]

Clean them up and put a small amount of oil or some kind of lubricant on them and they should click right in. Very common they might look clean but they're not.

[@user-rw9vt1bq5c]

I have a 2003 f250 I got a 171 and my truck will run good for awhile then It starts to losses power. If turn off the motor and restart it the problem goes away from awhile. Any suggestions

[@5.0Licks]

I recommend a fuel pressure test sounds like a weak fuel pump. But I would start checking for cheaper options such as the air filter, fuel filter , or fuel pressure regulator.

[@DeestarMusic55]

My Excursion is doin the exact same did you find the issue

[@wildmanmark12]

I have a 2006 ford freestyle. Had new cats installed and now the scanner reads cat 1 and 2 are running lean. And the car now burns more gas. Any idea what the issue is and how I can get I fixed.

[@swftflip]

Reset the A/F Trim

[@wildmanmark12]

@swftosrs any idea where the reset switch is located. I did see an icon just below and to the right where the glove box is that's got a fuel symbol with a line across it saying fuel reset but I don't see a switch.

[@lisaramirez6594]

I have a 2011 v4 escape limited. I changed the MAF and the downstream o2 sensor and also the fuel pump. I am now getting the p0171 code. I don't know what else to do. Please any help would be greatly greatly appreciated. Thank you.

[@nicolascaballero5890]

Fuel filter try that

[@brandonbranham7879]

Also have walmart run a fuel treatment through your vaccuum lines after the filter change...

[@flowersfam3462]

I was watching your video so glad I saw it because I just got codes PO125, PO401, PO402, PO1131, PO1151, PO171, PO174, PO305 I know that you didn't talk about all of the codes that I received, but I was wondering if you have other videos that would help me with them. I have a 2000 ford expedition 4.6L V8 Triton XLT 4WD and was hoping you had a video on a vehicle like mine with these code issues. I've already replaced my air filter and used the mass air flow spray to clean the sensor. Just going down the list and checking off the codes that showed up. I'm about to do my spark plugs and coils since I did receive misfire codes on 1 and 5. Just trying to go down the code list and do what I need to do with my vehicle. As a female, I've learned a lot by watching videos so I can save money and know how my vehicle works. Thanks for any information you can give me.😊

[@Coldsoldiers84]

I have a 2007 mercury Montego 3.0 I changed spark plugs and coil packs now I have a p0171 code I changed the air filter the MAF sensor and the pcv valve I also replaced the intake manifold gaskets upper and lower and I drove 243 miles now the check engine light is on what can it be I also checked for vacuum leaks I didn’t find any it’s driving me insane

[@Jksnatcher]

Same except I have a f150 did it stale at all or have rough idle

[@edwinhernandez4275]

Did you ever get this figured out? How is your fuel pressure?

[@kennybutler2426]

Hello,I was wondering if you figured your problem out.

[@jonmasters3113]

Left bank and right bank too rich fault