9 Causes and Fixes for a Nissan P0171 Error Code is “System Too Lean (Bank 1)”

Causes and fixes for a Nissan with a P0171 Error Code is “System Too Lean (Bank 1)”.
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Possible Causes:
Faulty mass airflow sensor
Vacuum leak
Failing fuel pump
Bad Fuel pressure regulator
Clogged fuel filter
Failing injectors
Bad oxygen sensors
Clogged catalytic converter.
Faulty (ECM/PCM)
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[@michaelslack6891]

My 2012 Sentra threw a P0171 lean condition code and ended up being the brand new Delphi AF10141 MAF sensor that I replaced the original 250,000 mile, 12 year old sensor with. If you replace MAF sensor on a 2007-2012 Sentra, buy a genuine Nissan sensor 22680-7S000. The Delphi sensor was $90+ and the genuine Nissan sensor was $210+

[@HumbleHotshot]

Good info here ! Thank, God bless you!

[@a.joegevara3519]

'16 Frontier 2.5, didn't get this code until I replaced O2 sensors, already replaced pcv & MAF sensor. My fuel pressure gauge is locked in a van that I lost (stolen?) the keys to. But thanks for the tips!

[@luisalbertoarteagatovar1984]

Thank you ser

[@michaelhoward4020]

It is also advisable to check out the PCV hose's especially if you are driving an older vehicle. Keep in mind that if you have a severe vacuum leak you will most likely also have a po 325 knock sensor code as well. I would advise you take a very close look at the Belloss IE the air intake tube between the air cleaner box and the throttle body because any Leaking there will cause a po 171 or po174 lean code.

[@seekingsoultribe]

Just bought a 2013 nissan rogue. Checked the computer and the past codes are a P0725 and P1701. Nothing current. I am having an rpm drop from 1500 to 1000 when ascending hills only. Happens for 1-2 seconds and then ascends normally. The check engine is not on. The codes are from the past. Any ideas?

[@ronaldoquintos1675]

May I add that fuel injector seal have been known to cause vacuum leak in my experience. Specially common on old cars. What happens is the rubber seal harden or even crack which cause vacuum leak.

[@michaelhoward4020]

If you spray carb cleaner around the seals it should reveal that.

[@datboydro2267]

And the brake booster

[@lovejazz]

You said a Mechanic will spray a flammable liquid to test vacuum ?

[@JulioV-qh1gh]

Can a bad spark plug make this code come up in g37

[@user-hb9vh5un8u]

I bought a nissan sentra 2015, and got p0171 after a week from driving it, it runs good but am scared of driving while check engine light is on.

[@sonnylopez6085]

You'll be aight!

[@lovejazz]

Can I remove the Mass Air flow Sensor and clean it ? If I dis connect it wil it effect anything else?

[@nonentitymusic]

No it’s just 2 screws and a clip usually

[@nonentitymusic]

Just don’t take it off while the engine is idling that’ll kill it

[@zayzay5460]

What ones would cause a crank but no start?

[@michaelhoward4020]

That issue could be lots of different things. Fuel pressure , low. Broken leaking fuel line connector at the fuel pump in side the gas tank. I assume you checked for a spark at the spark plugs? Some vehicles won't start if the Mas air flow sensor is completely gone bad, disconnect it and try to start the car. The list is long and I have experienced car like Cadillacs crank with a no start because the battery was able to crank but didn't have the juice to power up the pcm ecu . That one drove me nuts! I changed the battery and problem solved.

[@jammin1881]

I have a Pontiac vibe (Toyota matrix, Corolla ect) also have same / similar parts. It gives a PO171 code and was a bad intake manifold gasket. The old part wears down and the new gaskets have a thicker raised edge or lip. Spray carb cleaner near the manifold gasket and it changes the engine revs or sound. Thanks for posting!

[@PhilipMaguire-iy2th]

Only idel. Bad idel ?

[@Hello-pl2qe]

Autozone apparently resells previously installed maf sensors and sells them to you as new. The first one they handed me was in the box with scratches on it and a big white finger print from carb cleaner or something. The second one was admitted to be a return. Installing it did not fix my problem but obviously I have to wonder why the sensor had been returned by someone else. Fuck autozone.

[@zerteromusical9456]

Way too much i just changed the oxygen sensors all 4 on my chevy and still check engine light on 😢

[@noyourawsome2lol979]

Could be maf sensor

[@carlamayweather706]

No

[@madscientist6869]

F---k 😅