how to fix the P0301 code in my BMW 3 Series E90/E91 (2005-2012)?

Solution

1. Preparation

• Gather tools and parts needed.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool before beginning work.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket.
• Remove the engine cover if applicable.
• Disconnect the ignition coil connector.
• Remove the ignition coil from cylinder 1.
• Use a spark plug socket to remove the old spark plug.
• Inspect the spark plug for signs of wear or fouling (replace if necessary).
• Install the new spark plug and torque to manufacturer specifications (typically around 18-22 ft-lbs).
• Reinstall the ignition coil and reconnect the connector.

3. Replace Ignition Coil (if needed)

• Tools Required: Socket set, torque wrench.
• If the ignition coil shows signs of failure during inspection, remove the faulty coil.
• Install the new ignition coil and torque to manufacturer specifications (usually around 10-15 ft-lbs).
• Reconnect the ignition coil connector.

4. Inspect Fuel Injector

• Tools Required: Fuel injector removal tool (if required).
• Disconnect the fuel injector connector.
• Remove the fuel rail if necessary to access the injector.
• Inspect the injector for clogs; clean or replace if necessary.
• Reassemble the fuel rail and reconnect all connectors.

5. Test and Reassemble

• Reconnect the negative battery terminal.
• Start the engine and allow it to idle. Monitor for any misfire codes.
• If no codes return, reassemble any engine covers removed during the process.