how to fix P0171 code in BMW 3 Series F30/F31 (2012-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the vehicle battery to ensure safety.
• Allow the engine to cool down before beginning work.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  • Visually inspect all vacuum hoses for damage.
  • Use a smoke machine or carburetor cleaner to identify leaks.
  • Replace any damaged hoses or gaskets found during inspection.

3. Clean or Replace MAF Sensor

• Sub-steps:
  • Locate the MAF sensor in the air intake duct.
  • Disconnect the electrical connector and remove the sensor.
  • Clean the sensor with MAF cleaner spray and a lint-free cloth or replace with a new sensor if heavily contaminated.
  • Reinstall the MAF sensor and reconnect the electrical connector.

4. Check and Adjust Fuel System

• Sub-steps:
  • Connect a fuel pressure gauge to the fuel rail.
  • Turn the ignition to the "ON" position without starting the engine to check fuel pressure.
  • Compare the reading with manufacturer specifications; it should typically be between 50-60 psi (check specific values).
  • If pressure is low, inspect the fuel pump, filter, and injectors for issues. Replace any faulty components.

5. Inspect and Replace Intake Manifold Gasket (if necessary)

• Sub-steps:
  • Remove components blocking access to the intake manifold.
  • Unbolt the intake manifold and carefully lift it off.
  • Inspect the gasket for damage or wear, and replace it if necessary.
  • Clean mating surfaces before reinstallation and torque bolts to manufacturer specifications (typically around 16 Nm).