how to fix my BMW 5 Series G30/G31 (2017-2024) with P0303 misfire code

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, compression tester, fuel pressure gauge, multimeter.
• Disconnect the negative battery terminal to ensure safety while working on electrical systems.
• Gather necessary parts for replacement (if needed) such as spark plugs or ignition coils.

2. Inspect and Replace Spark Plug

• Remove the engine cover if applicable.
• Use a socket set to remove the spark plug from cylinder 3.
• Inspect the spark plug for wear or fouling.
  • If damaged, replace it with a new spark plug of the same specification.
• Torque the new spark plug to the manufacturer’s specified value (usually around 15-25 Nm).

3. Inspect and Replace Ignition Coil

• Disconnect the electrical connector from the ignition coil located on cylinder 3.
• Remove the ignition coil using the socket set.
• Inspect the coil for cracks or corrosion.
  • If faulty, install a new ignition coil and ensure it is seated properly.
• Reconnect the electrical connector securely.

4. Check Fuel Injector

• Disconnect the fuel injector connector for cylinder 3.
• Use a multimeter to check the resistance of the injector; it should fall within the manufacturer's specifications.
  • If the resistance is out of range, replace the injector.
• Reconnect the fuel injector connector after inspection or replacement.

5. Compression Test

• Remove the spark plug from cylinder 3 and install the compression tester.
• Crank the engine several times to obtain a compression reading.
  • If compression is below specifications (usually around 140-200 psi), further engine diagnostics may be required.