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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety while working on the vehicle.

2. Replace Spark Plug

• Tools Required: Spark plug socket, torque wrench, ratchet, dielectric grease.
• Remove the engine cover if applicable.
• Disconnect the ignition coil connector for cylinder 1.
• Remove the ignition coil using a ratchet and socket.
• Remove the spark plug using a spark plug socket.
• Inspect the old spark plug; if damaged, replace it with a new spark plug that meets OEM specifications.
• Apply a small amount of dielectric grease to the spark plug threads.
• Install the new spark plug and torque it to the manufacturer's specification (typically around 18 ft-lbs).
• Reinstall the ignition coil and reconnect the connector.

3. Replace Ignition Coil (if necessary)

• Tools Required: Ratchet and socket.
• If the ignition coil is found defective during inspection, remove it using a ratchet and socket.
• Install the new ignition coil for cylinder 1.
• Reconnect the ignition coil connector.

4. Check Fuel Injector (if necessary)

• Tools Required: Noid light or multimeter.
• Disconnect the fuel injector connector.
• Use a noid light to check for pulse; if there is no pulse, further inspect the wiring and ECU.
• If the injector is faulty, remove it and replace it with a new one.

5. Final Assembly

• Reinstall any removed components such as the engine cover.
• Reconnect the negative battery terminal.