How to Fix Engine Code P0174 Fast: 7 Proven Methods

When your check engine light pops on with the code P0174, it means your engine is running too lean on Bank 2—essentially, there’s too much air or not enough fuel in the mix. If left unaddressed, this issue can lead to rough idling, sluggish acceleration, and poor fuel economy.

Thankfully, with the help of a quality diagnostic scan tool like the Autel MaxiCheck MX900, you can get to the root of the problem quickly. Below are seven proven solutions (plus FAQs) to help you fix P0174 fast and restore your engine’s performance.

1. Check for Vacuum Leaks

One of the most common causes of code P0174 is a vacuum leak. If there's a leak in your intake system, it allows unmeasured air to enter the engine—throwing off the air-fuel mixture and causing a lean condition.

Start by inspecting:

• Vacuum hoses
• Intake manifold gaskets
• Throttle body seals

Look for cracks, holes, or loose fittings. Fixing even small leaks can make a big difference in performance and fuel efficiency.

Check the vacuum hose for vacuum leaks.

2. Clean or Replace the Mass Air Flow (MAF) Sensor

The MAF sensor measures how much air enters the engine. If it’s dirty or failing, it can send incorrect data to the engine control unit (ECU), leading to a fuel mixture that’s too lean.

Try cleaning the MAF sensor using a specialized cleaner, but if that doesn’t help, replace it. A properly working MAF sensor ensures accurate air-fuel ratios and prevents recurring P0174 codes.

3. Inspect the Fuel Injectors, Fuel Filter, and Pump

Restricted fuel flow can also trigger a lean condition. Dirty or clogged fuel injectors, an old fuel filter, or a weak fuel pump could prevent enough fuel from reaching the engine.
Here’s what to check:

• Clean the injectors if they’re dirty
• Replace a clogged filter
• Test and replace a failing fuel pump if pressure is too low

These steps help ensure your engine gets the fuel it needs to run smoothly.

Use a fuel pressure gauge to check whether the fuel pump outputs normal pressure.

4. Test the Oxygen (O2) Sensors

Oxygen sensors measure the amount of oxygen in the exhaust gases. Faulty readings—especially from the upstream (pre-cat) O2 sensor on Bank 2—can lead the ECU to make poor fueling decisions.
Signs of a failing sensor include:

• Poor MPG
• Emission test failure
• Check engine light codes like P0171 or P0174

Replace any sensors that are slow to respond or giving erratic readings. Autel scanners can help monitor real-time O2 sensor data during diagnosis.

5. Inspect the PCV Valve and Related Hoses

The Positive Crankcase Ventilation (PCV) system is another often-overlooked culprit. A stuck-open PCV valve or cracked PCV hose can introduce extra air, throwing off your engine’s calibration.
Check for:

• A rattling or stuck valve
• Cracked or collapsed PCV hoses

Replace the valve or hoses if needed. This low-cost repair can eliminate lean codes and improve idle quality.

The PCV system can cause issues if the valve sticks open or hoses crack, letting in excess air.

6. Check the Fuel Pressure Regulator

The fuel pressure regulator keeps fuel pressure within a precise range. If it’s faulty, your engine might not get enough fuel—causing a lean condition.
Watch for these signs:

• Hard starting
• Hesitation under load
• Lean codes like P0174

Use a fuel pressure gauge to test for proper pressure. If readings are too low, replacing the regulator may solve the problem.

7. Use an Autel Scan Tool for Accurate Diagnosis

Before you start replacing parts, use a professional-grade scan tool like the Autel MaxiCheck MX900 or MaxiSys MS906 Pro to pinpoint the exact issue. These tools allow you to:

• Read freeze frame data
• Monitor live sensor outputs
• Perform bi-directional tests

An accurate diagnosis saves time and money—and prevents throwing parts at the problem.

An Autel scan tool can diagnose the code and pinpoint its cause.

Final Thoughts

The P0174 code can be frustrating, but it’s fixable. Most causes boil down to unmeasured air or restricted fuel delivery. By following these practical steps—starting with a scan tool and working through the intake, fuel, and sensor systems—you can get your vehicle running properly again.

FAQs

Can a dirty MAF sensor trigger P0174?

Absolutely. A contaminated or faulty MAF sensor is a top cause of lean conditions. Try cleaning it first, and replace it if necessary.

How can I detect a vacuum leak?

Listen for hissing sounds around the intake system, and look for cracked hoses or gaskets. A smoke machine or carb cleaner spray can also help identify leaks.

Do I need to replace the oxygen sensor right away?

Not necessarily. Always test the sensor’s performance first with a scan tool. Only replace it if it’s clearly malfunctioning or sluggish.