how to fix P0171 code in my BMW 3 Series E90/E91 (2005-2012)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.

Tools Required:

• OBD-II scanner
• Fuel pressure gauge
• Multimeter
• Socket set
• Screwdrivers
• Cleaning spray (for MAF sensor)

2. Inspect and Repair Air Intake System

• Sub-steps:
  1. Visually inspect all vacuum hoses for cracks or disconnections.
  2. Tighten any loose clamps on the intake.
  3. Replace any damaged hoses or gaskets.

3. Check and Clean MAF Sensor

• Sub-steps:
  1. Locate the MAF sensor in the air intake duct.
  2. Carefully disconnect the MAF sensor connector.
  3. Remove the MAF sensor using a Torx screwdriver.
  4. Clean the MAF sensor with appropriate cleaning spray and let it dry.
  5. Reinstall the MAF sensor and reconnect the connector.

4. Test Fuel Pressure

• Sub-steps:
  1. Locate the fuel rail and attach the fuel pressure gauge.
  2. Turn the ignition to the "ON" position without starting the engine to check the pressure.
  3. Compare the reading to the manufacturer’s specifications (typically around 50-60 psi for BMW).
  4. If the pressure is low, inspect the fuel pump and filter for issues.

5. Inspect and Clean Fuel Injectors

• Sub-steps:
  1. Remove the fuel rail to access the fuel injectors.
  2. Inspect injectors for clogs or leaks.
  3. If necessary, use a fuel injector cleaner or replace the injectors.
  4. Reinstall the fuel rail and ensure all connections are secure.