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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool before starting work.

2. Inspect and Replace Ignition Coil

• Tools Required: Socket set, Torque wrench, Pliers
• Remove the engine cover if necessary to access the ignition coils.
• Unplug the electrical connector from the ignition coil for cylinder 1.
• Remove the bolt securing the ignition coil using a socket wrench.
• Carefully pull the ignition coil out of the spark plug well.
• If faulty, install a new ignition coil by reversing the removal steps. Ensure it is securely fastened and reconnect the electrical connector.

3. Inspect and Replace Spark Plug

• Tools Required: Socket set, Spark plug socket, Torque wrench
• Using a spark plug socket, remove the spark plug from cylinder 1.
• Inspect the spark plug for wear and fouling. If necessary, replace it with a new spark plug of the correct specification.
• Torque the new spark plug to the manufacturer’s specified torque value (usually around 20-30 Nm, check the specific value for your model).
• Reinstall the ignition coil on top of the new spark plug.

4. Check Fuel Injector

• Tools Required: Noid light or multimeter
• Connect the noid light to the fuel injector connector for cylinder 1.
• Crank the engine and check for flashing light, indicating injector operation.
• If no operation is detected, further inspect the wiring or replace the fuel injector.

5. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use an OBD-II scanner to clear the P0301 code from the ECU.