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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent any electrical issues.
• Ensure the vehicle is on a flat surface and the engine is cool.

2. Inspect Air Intake System

• Sub-steps:
  1. Visually inspect the air intake hoses for cracks or loose connections.
  2. Replace any damaged hoses or clamps.
  3. Ensure the air filter is clean; replace if necessary.

3. Clean or Replace MAF Sensor

• Tools Required: MAF sensor cleaner, screwdriver
• Sub-steps:
  1. Disconnect the MAF sensor connector.
  2. Remove the MAF sensor from the air intake duct.
  3. Spray the cleaning solution on the sensor element (do not touch).
  4. Allow it to dry completely before reinstalling.

4. Check Fuel Delivery System

• Tools Required: Fuel pressure gauge
• Sub-steps:
  1. Connect the fuel pressure gauge to the fuel rail.
  2. Turn the ignition to the "ON" position (do not start) and check pressure readings.
  3. Compare the readings to the manufacturer specifications. Replace the fuel pump or filter if pressure is low.

5. Inspect Intake Manifold and Gaskets

• Sub-steps:
  1. Remove the intake manifold cover (if applicable).
  2. Check for cracks in the manifold and inspect gaskets for wear.
  3. Replace any damaged gaskets or the intake manifold if necessary.

6. Reset the Engine Control Unit (ECU)

• Tools Required: OBD-II scanner
• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0171 code.
  3. Start the engine and monitor for any reoccurrence of the code.