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

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the negative terminal of the battery to prevent electrical shorts.
• Allow the engine to cool if it has been running.

2. Inspect and Replace Ignition Coil

• Tools Required: Socket set, Torque wrench
• Remove the engine cover for access.
• Disconnect the wiring harness from the ignition coil on cylinder 3.
• Remove the ignition coil mounting bolt and pull the coil out.
• Install the new ignition coil and torque the mounting bolt to manufacturer specifications (typically around 10 Nm).
• Reconnect the wiring harness securely.

3. Inspect and Replace Spark Plug

• Tools Required: Spark plug socket, Torque wrench
• Remove the ignition coil as previously described.
• Use a spark plug socket to remove the spark plug from cylinder 3.
• Inspect the spark plug for wear, carbon buildup, or oil contamination.
• Replace with a new spark plug (ensure gap is set according to manufacturer specs, usually around 0.7-0.8 mm).
• Torque the new spark plug to manufacturer specifications (usually around 23 Nm).
• Reinstall the ignition coil.

4. Inspect and Replace Fuel Injector (if necessary)

• Tools Required: Fuel injector tool set, Torque wrench
• Ensure fuel system pressure is relieved before proceeding.
• Disconnect the fuel line and electrical connector from the injector on cylinder 3.
• Remove the retaining clips and pull the fuel injector out.
• Install the new fuel injector and secure it with the retaining clips.
• Reconnect the fuel line and electrical connector.

5. Reassembly and Reconnect Battery

• Replace any engine covers removed during the process.
• Reconnect the negative terminal of the battery.
• Start the engine and check for any warnings or issues.