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

Solution

1. Preparation

• Gather tools and parts required.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery for safety.

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 system.
  3. Replace any damaged hoses.
• Tools Required: Screwdriver set, pliers.

3. Clean or Replace MAF Sensor

• Sub-steps:
  1. Disconnect the MAF sensor connector.
  2. Remove the MAF sensor from the intake pipe.
  3. Clean the sensor using MAF cleaner spray. Allow it to dry completely.
  4. Reinstall the MAF sensor and reconnect the connector.
• Tools Required: Torx screwdriver, MAF cleaner spray.

4. Check Fuel Pressure

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail.
  2. Turn the ignition to the “ON” position to prime the fuel system.
  3. Check the fuel pressure reading against the manufacturer’s specifications (usually around 50-60 PSI for BMW).
  4. If pressure is low, inspect the fuel pump and fuel filter for blockages or failures.
• Tools Required: Fuel pressure gauge.

5. Inspect Fuel Injectors

• Sub-steps:
  1. Remove the fuel rail to access the injectors.
  2. Inspect each injector for proper spray pattern (use a noid light if available).
  3. Clean or replace any clogged or malfunctioning injectors.
• Tools Required: Socket set, injector cleaner.

6. Clean Throttle Body

• Sub-steps:
  1. Remove the throttle body from the intake manifold.
  2. Clean the throttle plate and intake area with throttle body cleaner.
  3. Reinstall the throttle body and reconnect any sensors or hoses.
• Tools Required: Throttle body cleaner, socket set.