Troubleshooting Lexus RX350 P0174 Error Code

How to Fix the P0174 Error Code in Your Lexus RX350

If you own a Lexus RX350 and have encountered the P0174 error code, you're likely dealing with a system too lean (Bank 2) issue. This can be concerning as it affects the performance and efficiency of your vehicle. In this article, we'll guide you through the steps to diagnose and resolve this problem, ensuring your Lexus runs smoothly and efficiently.

Understanding the P0174 Error Code

The P0174 error code indicates that there is an imbalance in the air-to-fuel ratio, specifically that there is too much air or not enough fuel in the engine's bank 2. This can lead to various issues, including decreased fuel efficiency, engine misfires, and poor acceleration.

Shop Car Battery Now

Common Causes of P0174:

  • Vacuum leaks: Small holes or cracks in the vacuum hoses or intake manifold gasket.
  • Faulty Mass Air Flow (MAF) sensor: Incorrect readings from a dirty or failing MAF sensor.
  • Worn out oxygen sensors: Old sensors can send incorrect data to the engine's computer.
  • Fuel delivery issues: Problems with the fuel injectors, fuel pump, or fuel pressure regulator.

Step-by-Step Troubleshooting Guide

1. Check for Vacuum Leaks

  • Visual Inspection: Examine all vacuum hoses and the intake manifold for any signs of cracks or disconnections.
  • Smoke Test: A smoke test can help identify hard-to-see leaks. Introduce smoke into the intake system and look for smoke escaping from leaks.

Shop O2 Sensor Now

2. Inspect the Mass Air Flow Sensor

  • Clean the MAF Sensor: Sometimes, cleaning the MAF sensor with a specialized cleaner can resolve the issue.
  • Check MAF Sensor Connections: Ensure the sensor is properly connected and the wiring is intact.

3. Evaluate the Oxygen Sensors

  • Diagnostic Scan Tool: Use an OBD-II scanner to check the performance of the oxygen sensors.
  • Replace if Necessary: If the sensors are faulty, replacing them might resolve the error code.

4. Assess Fuel Delivery System

  • Fuel Pressure Test: Check the fuel pressure to ensure the fuel pump and regulator are functioning correctly.
  • Inspect Fuel Injectors: Look for clogged or leaking injectors that might be affecting fuel delivery.

Shop Fuel Cleaner Now

When to Seek Professional Help

If you've performed the above steps and the P0174 code persists, it might be time to consult with a professional. Mavyn offers both AI and human expert help services. You can chat with Mavyn GPT for quick troubleshooting tips or connect with a human expert who specializes in Lexus vehicles to get more personalized assistance.


Dealing with a P0174 error code in your Lexus RX350 can be frustrating, but with the right approach, it's a manageable issue. Start with basic checks like looking for vacuum leaks and examining the MAF sensor, and progress to more in-depth inspections if necessary. Remember, maintaining a proper air-to-fuel ratio is crucial for your vehicle's performance and longevity.

For further assistance, don't hesitate to use Mavyn's expert services. Whether you prefer AI-guided solutions or human expertise, Mavyn is here to help you resolve your automotive issues efficiently and effectively.