how to fix P0303 code in BMW X3 F25 (2011-2018)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool down completely.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket
• Remove the ignition coil from cylinder 3:
  1. Unscrew bolts securing the ignition coil.
  2. Carefully pull the ignition coil out of the spark plug well.
• Remove the spark plug:
  1. Use a spark plug socket to unscrew and remove the spark plug.
  2. Inspect the spark plug for carbon fouling, wear, or damage.
• Install a new spark plug:
  1. Apply anti-seize compound on the threads of the new spark plug (if recommended).
  2. Hand-tighten the new spark plug and then torque it to the manufacturer's specifications (typically around 20 Nm).

3. Inspect and Replace Ignition Coil

• If the spark plug is in good condition, check the ignition coil:
  1. Use a multimeter to check the primary and secondary resistance of the ignition coil.
  2. Replace the ignition coil if it is outside of the specifications.
• Reinstall the ignition coil:
  1. Position the coil back into the spark plug well.
  2. Secure it with bolts and reconnect the electrical connector.

4. Inspect and Replace Fuel Injector

• Check the fuel injector operation:
  1. Disconnect the fuel injector connector.
  2. Use a noid light to check for signal or use a multimeter to measure resistance.
• If the injector is faulty, remove it:
  1. Disconnect the fuel rail and remove any retaining clips.
  2. Pull the fuel injector out of the rail and replace it with a new one.
• Reinstall the fuel injector:
  1. Apply a small amount of engine oil to the O-ring of the new injector.
  2. Insert it into the fuel rail and secure it.

5. Reassemble and Test

• Reconnect the battery.
• Start the engine and check for any error codes or misfires.
• Monitor engine performance and ensure the check engine light is off.