Air & Fuel Mixture ControlOBD2 Codes

P0174 – Meaning, Causes, Symptoms, & Fixes

P0174 system too lean (bank 2)

What Does Code P0174 Mean?

  • P0174 definition: Bank 2 has too much air or not enough fuel.
  • Issue Severity: MODERATE– Extended driving with this code can cause internal engine damage.
  • Repair Urgency: Get this code fixed as soon as possible.
  • Diagnosis: It is important to complete the entire diagnostic process when diagnosing the P0174 code. This DTC can be triggered by a number of problems including a faulty MAF sensor, clogged fuel injectors, vacuum leaks, and more. 

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Combustion engines run most efficiently when they maintain an air-fuel mixture ratio of 14.7 parts air to 1 part fuel. When there are more than 14.7 parts air to 1 part fuel in the air-fuel mixture, a lean condition exists and code P0174 is triggered. The lean condition can be caused by a vacuum leak, which introduces more air into the air-fuel mixture, or by a weak fuel system, which does not input enough fuel into the air-fuel mixture. To keep the engine running properly, the powertrain control module (PCM) tries to compensate for the lean condition by injecting more fuel to the mixture in an effort to maintain the proper 14.7:1 ratio. When these adjustments become too large, code P0174 is triggered.

P0174 Causes

  • Dirty or faulty mass airflow sensor
  • Vacuum leaks – PCV hoses, vacuum hoses, intake manifold gasket.
  • Weak fuel pump
  • Clogged or dirty fuel injectors
  • Clogged fuel filter
  • Exhaust leak
  • Faulty oxygen sensor
  • Faulty air-fuel ratio sensor

P0174 Symptoms

  • Check Engine Light is on
  • Lack of power from the engine
  • Rough idle
  • Engine coughing
  • Engine misfiring

How Do I Fix Code P0174?

With a P0174 code, the first step is to get it properly diagnosed to figure out what is causing an issue with the air/fuel mixture. Using the live data function of the FIXD sensor and app allows you to read and analyze engine data to properly diagnose a P0174 code.

If the sensors are all reading correctly and you’re not comfortable further diagnosing this issue at home, we recommend finding a RepairPal-certified shop to pinpoint the problem and give an accurate estimate for repairs. 

These shops can not only help you figure out what’s going wrong before you waste time and money on the wrong parts, but they also offer a minimum 12-month, 12,000-mile warranty and stand behind all their estimates with guaranteed fair pricing.

> Find a RepairPal Certified Shop Near You

How Much Does It Cost to Fix Code P0174?

If you take your car to a shop for diagnosis, most shops will start with an hour of “diag time” (the time spent in labor diagnosing your specific issue). Depending on the shop’s labor rate, this typically costs somewhere between $75-$150. Many, if not most, shops will apply this diagnosis fee to any required repairs if you have them perform the repairs for you. From there, a shop will be able to give you an accurate estimate for repairs to fix your P0174 code.

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  • Upfront cost estimates
  • Minimum 12-month, 12,000-mile warranty
  • Fair price guarantee

Possible Repair Costs for P0174

When it comes to making repairs associated with the P0136 code, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair. 

  • Vacuum leak $100-$200
  • Clean MAF $100
  • Replace MAF $300
  • Fuel Pump $1300-$1700
  • Fuel pressure regulator $200-$400
  • Exhaust repair $100-$200 (if welded to repair)
  • Air fuel sensor or oxygen sensor $200-$300

DIY Steps to Diagnose Code P0174

If you’d like to try to fix code P0174 at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis. Complete diagnosis may require some specialized equipment beyond what the FIXD Sensor can provide, but for the most part, this diagnosis and repair can be attempted by beginner DIYers. 

DIY difficulty level: Intermediate

This repair requires mechanical knowledge and is not recommended for beginners.

Tools/parts needed (our top picks from Amazon):

  • FIXD
  • Mass air flow cleaner
  • fuel pressure testing gauge
  • Vehicle-specific repair manual
  • Screwdriver
  • Pliers
  • Soapy water

Scan your vehicle to verify P0174 is the only code present. If other codes are present, they must be addressed first.


Inspect all vacuum lines and hoses for leaks, and make sure they are properly connected. If a leak is present, you will hear a hissing sound, though it may be difficult to hear with the engine running. Lightly spraying soapy water on vacuum lines in areas of a suspected leak will make it easier to verify a leak: the engine will sputter or stall when water is sprayed on the leaking line. 


Remove the mass airflow sensor and clean the sensor using mass air flow cleaner or contact cleaner.


If check engine light code P0174 persists after you have reconnected and replaced all damaged vacuum lines and cleaned the mass airflow sensor, perform a fuel pressure test. If any components in the fuel system are failing, replace them as necessary.


If you confirm there are no vacuum leaks, have a clean mass airflow sensor, and your fuel system is functioning properly, check the exhaust for leaks before the Air Fuel Ratio Sensors or Oxygen sensors if you find any leaks have them repaired.


If at this point the vehicle is still setting the same code, you may have a more serious problem with your car’s oxygen sensor system, and you should bring the vehicle to a certified shop to have further diagnostic work performed.  

Common P0174 diagnosis mistakes

It is important to complete the entire diagnostic process when diagnosing P0174. Many people will replace the air fuel sensor or O2 sensor as soon as they get a bad reading, but the root cause is often a dirty or faulty mass airflow sensor or vacuum leak, thus causing the O2 or A/F sensor to read differently to compensate. Reading and analyzing fuel trims and the freeze frame data is the key to properly diagnosing P0174.

Still Need Help Fixing Code P0174?

If you’ve followed the steps above and are still experiencing issues with the engine’s air/fuel mixture and code P0174, please contact the FIXD Mechanic Hotline if you’re a FIXD Premium subscriber or find a RepairPal certified shop near you to get the right repairs at a fair price.


Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a ’91 GMC Syclone. #GirlDad #SaveTheManuals

Jeffrey N. Ross
Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a '91 GMC Syclone. #GirlDad #SaveTheManuals

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  1. This is awesome App. Anyone had a PO455 code reading?

    1. This the best device and service I’ve come across in a long time .Thanks to all at FIXD. RANDALL

      1. Excellent app.iam going for vacuum leak or oxygen sensor that light has been on for a week and now 0171ans0174 pop up trucks running fine at idle and great on highway.but could be intake manifold.let you know.God bless

        1. Hoping for a quick, affordable fix for you, Keith!

          1. Mine ended up being when they changed my air filter they ripped the seal on the air filter causing to much air then…. Click (check eng light) took to dealer ship because is was under warranty… Haha but not a air filter improperly installed.. $420.30 later.. Check Your Air Filter…

        2. I had both 0171 and 0174 come up and so before I started to panic, I decided to clean the MAF sensor myself. This eliminated code 0171 for me! Couldn’t believe how dirty it was. Now I can target bank 2 side to diagnose 0174.
          I have saved so much money, and time with this device and app!
          I’ve recommended it to everyone I know that owns a car.
          Thank you to the team at FIXD-you’re awesome!

    2. I have a 2003 nissan altima v6 se and was getting po171 and po174 so i change my maf sensor and it was ok for a day then the next it didn’t want to start later in the it did and them got a po300 and it was a rough idle and felt like mottor was working hard so i change all my spark plugs and coils and still the same problem now car hiccups well accelerating like at 40 or 60 and the p0171 comes om with kmow check eingen light just tge cod then cheak engine light gos on ant its the p0174 i check for imtake manifold leaks air leaks i spayed carb cleaner and know change of ideil and cheak the fule injectors with a screw driver and there all working do u thing it could be a fuel pump it tyrmd off on me like to times today

      1. If your car has over 150K its probably best to replace your Fuel filter (if it hasn’t been already) then clear your codes. If it returns, then go after your fuel pump. Inline fuel filters that get old can clog over time, restricting flow to the engine.

        1. Thanks for the tip, Sammy!

  2. Awesome app worth every penny

  3. CJ Marco
    Aug 2, 17:20 EDT

    I just wanted to say thank you for creating this wonderful item. I took my car to shop over a year ago and they told me I need a new intake manifold and it would be over 1500 dollars to fix it. I bought FIXD and plugged it in. It said to check the vacuum lines, fuel filter and mass flow air sensor. I did what the advice of the app said to do and I fixed my problems for less than 150 bucks. WOW. THE CAR IS GREAT. !!!! Just wanted to say thank you

    1. Hi Chuck,

      At FIXD we have the customer’s best interest in mind and we are thrilled to hear about your experience with your FIXD sensor. We love hearing personal stories from our customers, but don’t keep it to yourself, tell your friends!

      The FIXD Team

    2. I keep getting code p0174 only when car is warmed up and getting on the freeway! It’s the only code that keeps coming back. I reset the code it drives awhile no problem, then go get on freeway and it sets again. Toyota Camry 2003

  4. Ok what if im gettin a p0174 and a p0171 for both bank 1 and bank 2 runnin lean. Wich direction should i go first fuel or air

    1. Dis you ever figure out on going to fuel or air first?

    2. This the best device and service I’ve come across in a long time .Thanks to all at FIXD. RANDALL J.

    3. I am having the same problem. Getting both codes tells me it is not the O2 sensors. I have inspected most vacuum lines and they appear in good condition. I have also used fuel injector cleaner and cleaned the Mass Air Flow sensor. My next step is to replace the fuel filter and air filter – much cheaper than the fuel pump. Another possible cause could be a leak in the brake booster $$$$.

  5. Ok what if im gettin a p0174 and a p0171 for both bank 1 and bank 2 runnin lean. Wich direction should i go first fuel or air

    1. Are you running an aftermarket K&N type air filter? If so, that’s probably why, if not then dirty or faulty Maf, low fuel pressure or clogged injectors.

    2. When was the last time you replaced your fuel filter? if its been “years” go after that first, then clear your codes. If they resurface, then go after the fuel pump– if you’ve checked your running fuel pump measurements and they do not match (you can do this with your FIXD Sensor)

  6. Can a defective pcv valve cause p0174



    All these forced upon us sensors by the EPA and automakers lying about big hp gains. F U !!!!

    1. Most Probably You Are Right And I Agree With Your Conclusions

  8. Can more than one vehicle be programed into a FIXD unit?

    1. Yes. I have 5 vehicles on one FIXD Sensor

  9. Have a 2000 Cadillac Deville with codes P0171, P0172,P0443 and P00601 . Please where do I start first?

  10. Someone above complained about newer cars, and how annoying they are with codes flashing up. Nobody will disagree I’m sure. Back in the day when auto engines were less controlled, in Southern California, the smog was so thick that it was unhealthy to breathe outside air. On bad days you couldn’t even see clearly across a small street. The worst of all was that some parts of that smog contained nitrogen oxides. Those oxides can build up in your bloodstream and kill you if it adds up to enough concentrated amounts.
    Older cars were less expensive to maintain, were more simple. They burned inefficiently as well as real “dirty”. If nobody ever changed the way cars ran, now being at least 40 years later, everyone would either be stuck inside forever, or go outside and take a chance on choking to death.

  11. I have to agree. I’ve been driving for 45yrs and have had many vehicles. 67 Firebird, 68 Camaro, 79 Trans Am, 72 Chevy Pickup among many more. The aforementioned cars were by far the easiest to work on and fix. For a girl to be able to diagnose and fix her own car was awesome. Everyone thought so. Fast forward to married with children and new 96 mini van, problems were hell and haven’t gotten any easier. Always to the shop nowadays. This fixd app is the best thing since berry pie. Now I drive a 97 Ford F150 with 87, 302 miles and without this app I’d be back at the shop. Thank you FIXD TEAM for making this old ladies life a bit easier. Oh and the emissions part….happy to be able to breathe outside while I write this.

    1. *High five* to women fixing their own cars! LOVE hearing this Laurie! Thank YOU for the kind words. Cheers to many more years of simpler car care and successful tinkering 🙂

  12. Ok, I gotta po174 and the other port code. Injectors running lean, failed California’s stupid smog check. Added sea foam motor treatment and am going to clean the maf sensor right now. I’ll let you know what happens. Great app, btw.

    1. Glad to hear you’ve got some good things to try. Thanks and let us know how it goes!

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