Solving P0171 And P0174 Lean Check Engine Light On A Nissan Frontier

In this video I solved my P0171 or P0174 issue on my Nissan Frontier. This can be applied to Xterra and Pathfinder with the VQ40DE engine. This process can also be applied to many modern engines as well. I go through the steps of check the intake, vacuum lines, MAF sensor, 02 sensor, brake booster and catalytic converter. The issue I had was related to a cracked hose in my oil catch can which is connected to the PCV system on the engine.

[@Mexicanburrito137]

Good I saw this video, my frontier has 220k miles and the hose after the maf sensor has a crack in it. Great video

[@autoxadvice4159]

Glad you got yours fixed up. Thanks for stopping by and commenting.

[@SergioChavira]

Pathfinder 2014 has that code. This will be very useful to track the code later this morning. Thank you!

[@autoxadvice4159]

Hope you can track down the issue.

[@SergioChavira]

Yes! One of the hoses coming out of the air filter box was completely disconnected! It was under that cosmetic cover Nissan uses, not visible to the naked eye.

[@autoxadvice4159]

Glad you got it sorted.

[@ELEVOPR]

Another great video Buddy 🤜🏼🤛🏼 I'm about to tackle this job myself since I'm getting same Code P0171. Mine started to happen after the AC Guy took some lines out to replace the O rings on AC lines. Maybe it was a Koinkydink? Maybe not. Either way I bought a Set of PCV Hoses/lines kit, as well as the PVC itself. Also got the updated mass airflow Sensor, Just Incase, while I was at it I got the Genuine OEM Engine Air Intake assembly that comes with both Accordion style hoses, after mass air flow and Throttle body as well. one is looking a little pale in color as well and for $99 shipped , why not 🤷🏻‍♂️ The reason I have those parts is because the truck is in PR and sometimes it takes weeks to order the parts if not in Stock 🤦🏻‍♂️ Also the truck only has 42k on it even though it's an 06 CC SE I'll swing back and update once I figure out what's the issue. Any extra good parts left over that are good I can either sell or keep for future issues. Thanks again for such a detailed video. 👍🏻

[@autoxadvice4159]

Hopefully you have fixed your P0171 issue. Also, check that flex boots on the intake they are known to crack.

[@ELEVOPR]

@@autoxadvice4159 Ok, so far my issue was the Oxygen Sensor on bank one, I have a leak in my passenger side valve cover and it was dripping right onto the Oxygen sensor wires, not sure if that cause the system is running to rich? The oxygen sensor was Super black at the top of it the driver side oxygen sensor was clean as a whistle.

[@ELEVOPR]

@@autoxadvice4159 I put in a whole new intake with new boots as well as mine had a lot of stress cracks in the boots and the intake was a bit pale, so why not 🤷🏻‍♂️ My problem ended up being the Oxygen sensor upstream in the passenger side. When I removed the sensor it was pitch black and covered in black soot. The drivers side was nice and clean compared to the passenger side. fuel trims were out of wack before the Oxygen sensor was removed. Now they are Stable with the New Bosch Wide band Oxygen Sensors. So far so good, it's been two days and I have driven over 100 miles and no Check Engine Light. I'll update if anything changes. Thanks again for the video 👍🏻

[@autoxadvice4159]

Good job getting it sorted.

[@rebekahrios2663]

How do I know which o2 sensor is bad. I have a 2010 Nissan frontier. Check engine light indicating P0171. Stating Fuel system lean bank 1. Also at the top of the reader, it indicated CAT and O2sensor. Truck shut off on me at a red light for the first time, it does turn back on eeeeventually. I would appreciate your advice

[@autoxadvice4159]

You should start with the less expensive parts first. The video goes through how you check which first and then it goes into the cat and 02s. Bank 1 is riders side. Which 02 that is detecting too much oxygen will depend on testing it with a scanner. Now there could be low fuel pressure, bad injectors, or clogged fuel filter. But if your truck is running just fine during acceleration and it's not jumping all over the place when idling then you could probably eliminate those and it's why it's important to start looking at the rest stuff first like the intake, cleaning the CAI sensor and checking vacuum lines.

[@Slavic_Boer]

I have this. Didn't notice anything during driving. when I shut it off, it sounded "heavier" idling down. Eventually when driving home, the CEL started to flash erratically. So now I parked it until I take it to my mechanic in a few days.

[@autoxadvice4159]

You mean you have the p0171 code? Usually a flashing CEL would mean misfire and it could be connected if you have a major leak and too much air coming into the engine.

[@Slavic_Boer]

@@autoxadvice4159 Both P0171 and P0174. Running fine. Just when I turn it off it feels "heavier". I'm going to borrow a scan tool tomorrow to verify that my manual extraction of codes is correct.

[@autoxadvice4159]

@Slavic_Boer that's a good place to start to see what the scanner says. Let me know.

[@Slavic_Boer]

@@autoxadvice4159 Same codes showed, so I cleared it, Then I inspected what I could up until the throttle body. Tightened up all the hose clamps. I noticed the air filter cover wasn't locked in the back corner. Then I saw the air filter wasn't seated in flush. About 1600 miles ago I had an oil change done. I'll have to assume whoever checked, didn't install it properly. Maybe he thought he did. I then went for a drive and nothing came up. See what happens. I'll keep my appointment regardless until I know for sure.

[@autoxadvice4159]

The flex boot on the intake can crack if it gets too old. Check that as well.

[@mikecleveland823]

That is coming from the pre-cat sensor, so it wouldn't be an issue with the catalytic converter.

[@autoxadvice4159]

A cat can become clogged and create back pressure and have more air build up over the 02. It's one of the reasons to check the cat. Since there are two cats and either one can become clogged.

[@StationRussification]

No U could have an air leak anywhere that includes the exhaust

[@falconthree3815]

Can I use the green test cap to connect my smoke can to thank you for any help😎😎😎😎

[@autoxadvice4159]

For emissions yes.

[@golfcon]

Great explanation….I have a p0171 code a bad rotten egg smell from the exhaust….maybe it is the CATs for my g35

[@autoxadvice4159]

Yeah rotten eggs isn't a good sign. You should still go through and check the easy stuff as it's possible to have multiple issues. Nothing like buying parts and hoping your issue is fixed only for the same same code to pop up again. Thanks for stopping by and checking out the video.

[@StationRussification]

Generally an air leak drives the O2 lean & the Engine Controller fattens it up w/fuel so the Cat is not happy ... U could have deeper issues as well. This code is basically saying there is slightly too much air & most likely an intake side leak that could be found by lightly spraying water around till U hear it sucking up BUT really a pro should do this.... also a small exhaust leak could cause this fault but usually U will get a most sophisticated fault leading U there.

[@krperry2007]

Hi, Do you see much oil in the catch can?

[@autoxadvice4159]

I change oil every 5k miles. I will see about a 1/4 in to 1/2 in. In the can.

[@krperry2007]

@@autoxadvice4159 Well that's not nothing... How much is the oil level down when you change oil? Thanks!

[@autoxadvice4159]

Honestly i see very very little difference that i could even detect. I have never had to add any oil to this truck. The Frontier and my Mazda 6 burn little and I'm happy about that.

[@krperry2007]

@@autoxadvice4159 I have an 08 Frontier with 153,000 miles I don't add oil nor have I had a leak. I just had to change an ign. coil.

[@phambruhh7003]

what hose is @ 4:22

[@autoxadvice4159]

I think you found a mistake in my video of it's the hose you are talking about. The one where I say it's a vacuum line and it's not. It's an evap line and if that is cracked you would get an evap leak code not an intake code.