how to fix P0171 code on my BMW 3 Series G20/G21 (2019-2024)

Solution

1. Preparation

• Gather tools: OBD-II scanner, fuel pressure gauge, multimeter, socket set, MAF cleaner, and vacuum gauge.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Ensure the vehicle is on a level surface and securely lifted if needed.

2. Inspect and Repair Air Intake System

• Sub-step 1: Remove the engine cover and intake ducts to access the air filter.
• Sub-step 2: Check the air filter for clogs and replace it if necessary.
• Sub-step 3: Inspect all intake hoses for leaks; replace any damaged hoses.
• Sub-step 4: Ensure all clamps are tight and secure.

3. Check and Replace MAF Sensor

• Sub-step 1: Disconnect the MAF sensor connector.
• Sub-step 2: Remove the MAF sensor using a socket set.
• Sub-step 3: Clean the sensor with MAF cleaner; if it is damaged, replace it with a new one.
• Sub-step 4: Reinstall the MAF sensor and reconnect the electrical connector.

4. Test Fuel Pressure

• Sub-step 1: Locate the fuel rail and connect the fuel pressure gauge.
• Sub-step 2: Turn the ignition to the "ON" position (do not start the engine) and check the pressure reading against manufacturer specifications.
• Sub-step 3: If the pressure is low, inspect the fuel pump and fuel filter for issues, and replace as necessary.

5. Inspect Vacuum Lines

• Sub-step 1: Inspect all visible vacuum lines for cracks or disconnects.
• Sub-step 2: Use a vacuum gauge to test for proper vacuum levels.
• Sub-step 3: Replace any damaged vacuum lines.