how to fix P0171 and P0174 codes in BMW 5 Series F10/F11 (2010-2017)

Solution

1. Preparation

• Gather necessary tools and parts.
• Park the vehicle on a level surface and ensure the engine is cool.
• Disconnect the battery to prevent electrical shorts.

2. Inspect Air Intake System

• Tools Required: Socket set, flashlight
• Remove the air intake duct to access the air filter and MAF sensor.
• Inspect the duct and connections for any cracks or loose fittings.
• Clean the MAF sensor using MAF cleaner spray; do not touch the sensor elements directly.
• Reinstall the air intake duct securely.

3. Check for Vacuum Leaks

• Tools Required: Smoke machine (or carburetor cleaner for testing)
• With the engine running, use a smoke machine to introduce smoke into the intake system to identify leaks.
• Alternatively, spray carburetor cleaner around vacuum lines and intake manifold; listen for RPM changes.
• Replace any damaged vacuum hoses or gaskets.

4. Inspect and Test Fuel System

• Tools Required: Fuel pressure gauge
• Remove the fuel pump fuse and start the engine to relieve fuel pressure.
• Connect the fuel pressure gauge to the fuel rail test port.
• Turn the ignition on (do not start) and check the pressure against manufacturer specifications (typically around 50-60 psi).
• Replace the fuel filter if clogged, and ensure the fuel pump is functioning properly.

5. Replace Oxygen Sensors (if needed)

• Tools Required: O2 sensor socket, torque wrench
• Locate the upstream and downstream oxygen sensors for both banks.
• Disconnect the electrical connectors and remove the sensors using the O2 sensor socket.
• Install new oxygen sensors, ensuring correct torque (usually around 30 Nm).
• Reconnect electrical connectors.

6. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear the trouble codes from the system.
• Start the engine and allow it to reach operating temperature.