Maintenance Tips, Tricks And Hacks For Your Vehicle

P0174 OBD-II System Too Lean Bank 2 Trouble Code




The P0174 code is an OBD-II trouble code that stands for “System Too Lean (Bank 2) which signifies that your vehicle’s air-fuel ratio is excessively lean (there is more air than fuel in the combustion chamber).

In this article, I will be talking about the P0174 trouble code, its symptoms, causes, and how to fix it.

What Does The P0174 Code Mean?

P0174 OBD-II System Too Lean Bank 2 Trouble Code

A P0174 trouble code means that either too much air or not enough fuel is entering the engine’s second half. As a result, the air-to-fuel ratio within the engine is incorrect.

The ideal air-fuel ratio for the majority of automobiles is 14.7 parts air to one component gasoline.

When your vehicle saves the trouble code P0174, it indicates that the disparity between the amount of air and fuel entering the engine is so great that the fuel injectors cannot remedy the issue.

There is a greater problem than a modest increase in fuel can fix.

Often, a P0174 trouble code indicates a vacuum leak or fuel pump issue. The long-term lean operation might cause your engine to overheat, run dry, or sustain severe internal damage.

P0174 is not a code to be disregarded or taken lightly.

(Related: P0171 OBD-II System Too Lean (Bank 1) Trouble Code)

Which Models Are Affected By The P0174 Code

MakeAffected By P0174 Code

What Are The Possible Causes of the P0174 Code?

A P0174 trouble code is caused when the vehicle’s computer detects an improper air-to-fuel ratio in the combustion chamber e.i more air than fuel in the combustion chamber.

A defective MAF sensor or a vacuum leak is the most prevalent cause of the P0174 code. Low fuel pressure can also be caused by a weak fuel pump or a blocked fuel filter.

Here are the possible causes of the P0174 trouble code:

  • Dirty or defective mass airflow (MAF) sensor
  • The leaks from the vacuum system
  • Dirty or clogged fuel injectors (clean them)
  • Defective oxygen sensor
  • Faulty fuel pressure regulator
  • Clogged fuel filter (clean it)
  • The fuel pump is weak
  • Defective positive crankcase ventilation (PCV) valve
  • Brake booster leaking
  • Defective valve cover gasket

What Are The Common Symptoms of The P0174 Code?

The most common P0174 trouble code symptoms are a check engine light and poor engine performance. You may also experience hiccups and rough acceleration.

Here are the most common symptoms of the P0174 trouble code:

  • The check engine light
  • Fuel consumption has increased
  • High or rough idle
  • Decrease in the ability to accelerate
  • Decreased engine performance

Is It Safe To Drive With a P0174 Code

Yes, it is safe to drive with the P0174 trouble code but only for a short distance. Driving with the P0174 trouble code does not immediately damage your vehicle’s components.

But, if you continue to drive with a lean-burning engine, it may overheat and destroy internal engine components. Running rich is always preferable to running lean because the additional fuel keeps the engine cool.

You may want to neglect a P0174 code for a while since you may not instantly detect other vehicle problems.

An issue with the air-fuel mixture, on the other hand, might cause severe problems with the vehicle’s drivability since the engine is not receiving enough gasoline.

Avoid performing full acceleration pulls if this trouble code is displayed. Instead, drive gently to the workshop and first conduct a thorough diagnosis.

In addition, some of this problem’s causes may have their own potentially dangerous side effects. For instance, an exhaust leak can expose you to carbon monoxide pollutants that are fatal.

How To Diagnose The P0174 Code

Here is how to diagnose the P0174 trouble code:

  1. Connect an OBD2 Scanner and search for any other trouble codes that may indicate another damaged component.
  2. Connect an EVAP smoke machine to the system and pressurize it to locate any intake or vacuum leaks. If you identify any leaks, fix them and clear the codes.
  3. Check visually if you do not have an EVAP smoke machine or visit a workshop that does have one. That greatly aids in the diagnosis.
  4. Examine the MAF sensor and thoroughly clean it with an electronic cleaner.
  5. Reinstall the MAF sensor and clear the trouble codes. Continuing with the troubleshooting if the issue persists.
  6. Examine the MAF sensor values with an OBD2 scanner. If something appears odd, the MAF sensor should be replaced.
  7. Check the fuel pressure at idle and during driving by connecting a fuel pressure gauge to the fuel rail. If you observe a low fuel pressure – replace the fuel filter or fuel pump.
  8. Examine the function of the positive crankcase ventilation (PCV) valve and the evaporative emission control system (EVAP) purge control valve if the problem remains after attempting the previous solutions.
  9. If there are no issues with the positive crankcase ventilation (PCV) or evaporative emission control system (EVAP) Valve, you should replace the O2 sensor on Bank 2.

(Related: P0135 OBD-II O2 Sensor Heater Circuit Bank 1 Sensor 1 Trouble Code)

Most Common Mistakes When Diagnosing The P0174 Code

The most common mistakes when diagnosing the P0174 trouble code are:

  • Changing a component without first determining that it is defective through testing.
  • Failing to examine the intake system for tears or leaks.

How Much Does It Cost To Repair P0174 Code

Cleaning the MAF sensor costs around $25 if you do it, or $60 for a mechanic to do it.

Replacing the fuel filter costs $25 if you do it, or $90 if a mechanic does it.

O2 sensor costs between $39.98 and $161.77

MakeP0174 CodeRepair Cost
ToyotaYes$25 – $161.77
NissanYes$25 – $161.77
ChevroletYes$25 – $161.77
BMWYes$25 – $161.77
AudiYes$25 – $161.77
BuickYes$25 – $161.77
MercedesYes$25 – $161.77
GMCYes$25 – $161.77
SuzukiYes$25 – $161.77
TataYes$25 – $161.77
LexusYes$25 – $161.77
MazdaYes$25 – $161.77
MitsubishiYes$25 – $161.77
KiaYes$25 – $161.77
JeepYes$25 – $161.77
FiatYes$25 – $161.77
HondaYes$25 – $161.77
HyundaiYes$25 – $161.77
OpelYes$25 – $161.77
FordYes$25 – $161.77
FiatYes$25 – $161.77
PeugeotYes$25 – $161.77

What Repairs Can Fix The P0174 Code?

Repairs that can fix the P0174 trouble code are:

  • Clean or replace the mass air flow (MAF) sensor
  • Replace the defective oxygen sensor
  • Repair the leaks in the vacuum system
  • Change the fuel filter
  • Change the fuel pump
  • Replace the valve cover gasket
  • Replace the positive crankcase ventilation (PCV) valve
  • Change the brake booster

How To Fix The P0174 Code

Below are some steps that you should take to fix the P0174 trouble code

  • Replace the mass air flow (MAF) sensor
  • Reprograming or replacing the powertrain control module (PCM)
  • Replace the defective fuel injectors
  • Changing the valve cover gasket
  • Clean the mass air flow (MAF) sensor
  • Clean the exhaust gas recirculation (EGR) system
  • Change the defective oxygen sensor
  • Replacement of the defective vacuum lines
  • Replacing the faulty brake booster
  • Replacement of the faulty or damaged positive crankcase ventilation (PCV) valve
  • Repairing exhaust leaks

In Conclusion

When the air-fuel mixture for bank 2 is so lean that the electronic control unit (ECU) cannot compensate by modifying the fuel trims, the P0174 trouble code is set. This is determined by the ECU utilizing a signal from the oxygen sensor.

With a P0174 trouble code, you may encounter a rough idle, hesitation during acceleration, misfire, or overall poor engine performance. Similarly to any other trouble code, the check engine light will illuminate.

Typically, a lean mixture is caused by vacuum or boost leaks, fuel delivery problems, or inaccurate MAF measurements. The P0174 code can sometimes be caused by a defective oxygen sensor or a stuck-open PCV valve.



Vide Polowenski, Senior Mechanic

The information in this article is current and up-to-date in accordance with the latest mechanic SOPs.

Please take the time to leave a comment if this article has helped you in any way, you need additional help, or you have a suggestion.

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