how to fix P0301 misfire 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 during repairs.

2. Inspect and Replace Spark Plug

• Tools Required: Spark plug socket, ratchet, torque wrench.
• Remove the engine cover if necessary.
• Unscrew and remove the spark plug from cylinder 1.
• Inspect the spark plug for wear, carbon buildup, or damage.
• If needed, replace the spark plug with a new one, ensuring it matches the manufacturer's specifications.
• Torque the new spark plug to 18 lb-ft (25 Nm).

3. Inspect and Replace Ignition Coil

• Tools Required: Socket set.
• Disconnect the electrical connector from the ignition coil.
• Remove the ignition coil from cylinder 1.
• Inspect for cracks or damage; replace with a new ignition coil if necessary.
• Reinstall the ignition coil and reconnect the electrical connector.

4. Test and Replace Fuel Injector (if needed)

• Tools Required: Noid light or multimeter.
• Disconnect the fuel injector harness from cylinder 1.
• Connect the noid light to the fuel injector connector to ensure it is receiving power.
• If the noid light does not blink, check the wiring and replace the injector driver circuit if necessary.
• If the injector is faulty, remove it and replace it with a new one, ensuring it is secured properly.

5. Reassemble and Clear Codes

• Reinstall any components removed during the repair process.
• Reconnect the negative battery terminal.
• Use an OBD-II scanner to clear the P0301 code from the vehicle’s computer.