P0174 – Meaning, Causes, Symptoms, & Fixes

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. 
• Common Reason: Code P0174 is often related to a vacuum leak.

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.

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

STEP 1: USE FIXD TO ENSURE NO OTHER ENGINE CODES ARE PRESENT.

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

STEP 2: INSPECT VACCUM LINES. 

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. 

STEP 3: INSPECT MAF SENSOR.

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

STEP 4: CHECK FUEL PRESSURE

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.

STEP 5: INSPECT EXHAUST SYSTEM.

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.

STEP 5: CONSULT A PROFESSIONAL.

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.

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