The proper supply of air and fuel into the engine ensures the efficient working of the vehicle. The combustion of the lean air-fuel mixture can be created by a vacuum leak that draws more air into the air-fuel mixture. The lean condition may also occur due to a bad fuel injector that isn’t injecting sufficient fuel into the mixture. Whenever the powertrain control module (PCM) detects a lean condition in cylinder bank 2, it triggers the P0174 code. This article mainly explains the P0174 code symptoms, its causes, and how to fix it.
P0174 Code Definition
The P0174 trouble code stands for “System Too Lean (Bank 2).”
What does P0174 Code Mean?
The P0174 code indicates that your powertrain control module (PCM) detects a lean running condition.
The P0171 and P0174 trouble codes indicate the lean running conditions. The P0171 trouble code triggers when PCM detects a lean condition in cylinder bank 1, while P0174 triggers when PCM detects a lean condition in cylinder bank 2.
A lean condition occurs when your vehicle’s air-fuel mixture has too much air and insufficient fuel.
The vacuum leaks may also lead to lean conditions. The vacuum leaks may introduce more air into the air-fuel mixture or by a weak fuel system which leads to a lean condition. To ensure the efficient working of your vehicle, your PCM also assists in compensating for the lean condition by injecting more fuel into the mixture in an effort to maintain the proper 14.7:1 ratio.
However, when your PCM can’t fix the lean condition, it triggers the P0174 code.
Causes of P0174 Code
- Damaged or dirty MAF sensor
- A leaky PCV valve
- Weak fuel pump
- Bad air-fuel ratio sensor
- An air leak after the MAF sensor, such as a damaged intake manifold gasket
- Improper or insufficient fuel pressure
- Clogged or damaged fuel injector
- Dirty fuel filters
- Bad O2 sensor
- Exhaust leaks
- A vacuum leak such as intake manifold gasket, vacuum hoses, and PCV hoses.
- Brake booster leaks
- Problems with PCM
Read More: Bank 1 Vs Bank 2
Symptoms of P0174 Code
- Illuminated check engine light
- Engine misfiring
- A clear reduction in the engine power
- Engine stalling
- Rough idling
- Engine coughing
- Higher fuel consumption
Read More: P0356 Code Symptoms and Causes
How to diagnose the P0174 Code
- Use a scanner tool to confirm the presence of the P0174 code. If other codes are present, you should fix them first.
- Perform a fuel pressure test to check the fuel pressure
- Inspect the intake system for leaks
- Inspect the vacuum lines for leaks
- Test the relevant O2 sensor by using a multimeter or scan tool
- Check the valve cover for a leak or worn hoses
- Use a multimeter or scan tool to test the MAF sensor
- Inspect the exhaust system for a leak before the O2 sensors
- Check the PCV valve for damage or corrosion
- Inspect the powertrain control module (PCM). If your PCM is faulty, replace it.
Common P0174 Code Diagnostic Mistakes
- Replacing the unnecessary components
- Replacing a component without testing it
- Not inspecting the vacuum system and exhaust system for leaks
- Not clearing the PCM memory after fixing the error codes
What repairs can fix the P0174 Code?
- Replacing the MAF (mass air flow) sensor
- Replacing the faulty EGR valves
- Cleaning the MAF sensor
- Cleaning the EGR system
- Replacing the bad O2 sensor
- Fixing the vacuum leaks
- Replacing the faulty or damaged PCV valve
- Fixing the exhaust leaks
- Replacing the faulty fuel injectors
- Replacing the damaged brake booster
- Replacing the damaged vacuum lines
- Replacing valve cover gasket
- Reprograming or replacing the PCM
Repair Cost for P0174 Code
To fix the P0174 trouble code, you need one or more of the below-given repairs:
| Parts | Repair Cost |
|---|---|
| Vacuum leak repair | $90 to $220 |
| MAF sensor cleaning | $80 to $110 |
| Fuel Pump replacement | $220 to $1,090 |
| MAF sensor replacement | $100 to $320 |
| Fuel pressure regulator replacement | $280 to $480 |
| Exhaust gas leak repair | $120 to $300 |
| Spark plug replacement | $180 to $270 |
| O2 sensor replacement | $320 to $410 |
FAQ Section
How serious is the P0174 code?
The P0174 code is not a serious code. You shouldn’t drive with this code for a long time. This code may lead to various drivability problems such as engine stalling, rough idle, or poor acceleration.
Can I drive with the P0174 code?
Yes, you can drive, but driving a vehicle for a long distance is not recommended with the P0174 code. You may face different drivability issues when you drive a vehicle with the P0174 trouble code. Driving with this code doesn’t immediately damage the parts of your vehicle.
However, continuing to run the lean engine may cause engine overheating, engine stalling, and even damage to many other inner parts of the engine. Running rich is always preferable to running lean, as excess fuel will keep the engine cool.
Can an exhaust leak cause a P0174 code?
The vacuum leak is one of the major causes of the P0171 and P0174 codes. Your powertrain control module triggers these codes when it senses too much oxygen in the exhaust. The lean code is set due to readings of excess air in the exhaust.
How do I fix error code P0174?
You need one or more below given repairs to fix the code P0174:
- Replacing the MAF sensor
- Reprograming or replacing the PCM
- Replacing the faulty EGR valves
- Replacing the faulty fuel injectors
- Replacing valve cover gasket
- Cleaning the MAF sensor
- Cleaning the EGR system
- Replacing the bad O2 sensor
- Replacing the damaged vacuum lines
- Fixing the vacuum leaks
- Replacing the damaged brake booster
- Replacing the faulty or damaged PCV valve
- Fixing the exhaust leaks
Can a bad O2 sensor cause a P0174?
A P0171 code with an O2 sensor reading always means a few things. The real issue may not be a faulty oxygen sensor, but dirty fuel injectors, low fuel pressure, or vacuum leaks can cause the engine to run lean.
Can a dirty air filter cause code P0174?
Yes, a dirty air filter is one of the major causes of a lean condition, but it is rare and does not usually cause a lean condition on its own. A dirty air filter releases unfiltered air into the mass air flow sensor, and dirt accumulates in the sensor. This stops the filter from sending the correct information to PCM, which ultimately triggers the thin code.
Can P0174 cause a misfire?
Normally, a P0174 code may lead the poor performance of your engine, which the driver may notice as an engine stalling, a misfire, a lack of power, or even a high idle.
Can a fuel pump cause a P0174 code?
Yes, a vacuum leak or an issue with the fuel pump is the usual cause of the P0174 code.
Which oxygen sensor is P0174?
P0174 is set due to the engine bank 2 “upstream” O2 sensor. The O2 sensor warns your system when the condition is too lean meaning there’s too much air in the exhaust.