why does my BMW 5 Series G30/G31 (2017-2024) have a check engine light with P0171 code?

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the negative terminal of the battery to prevent electrical shorts.

Tools Required:

• OBD-II scanner
• Vacuum gauge
• Fuel pressure gauge
• Socket set
• Torque wrench
• Multimeter
• Cleaning supplies (MAF cleaner)

2. Inspect Air Intake System

• Remove the engine cover (if applicable) to access the air intake.
• Inspect hoses and connections for cracks or loose fittings.
• Replace any damaged hoses or clamps.
• Reconnect the air intake system.

3. Clean MAF Sensor

• Locate the MAF sensor in the air intake duct.
• Carefully remove the sensor following manufacturer guidelines.
• Clean the sensor using MAF cleaner and allow it to dry completely.
• Reinstall the MAF sensor and ensure it is securely connected.

4. Check Fuel Pressure

• Connect the fuel pressure gauge to the fuel rail.
• Turn the ignition to the "ON" position (do not start) and observe the pressure reading.
• Compare the reading to the specifications found in the service manual. If pressure is low, check the fuel pump and filter.

5. Inspect Fuel Injectors

• Remove the fuel rail with the injectors attached (ensure to relieve fuel pressure first).
• Inspect the injectors for clogs or leaks.
• Clean or replace any faulty injectors as needed.
• Reinstall the fuel rail and torque to specifications.

6. Verify Exhaust System

• Inspect the exhaust system for leaks, particularly around the manifold and catalytic converter.
• Repair any leaks found to ensure proper back pressure and readings.