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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

Tools Required:

• OBD-II scanner
• Socket set
• Torque wrench
• Compression tester
• Fuel injector cleaning kit (if applicable)

2. Inspect and Replace Spark Plug

1. Remove Engine Cover: Unscrew and remove any engine cover to access the ignition components.
2. Disconnect the Ignition Coil: Unplug the electrical connector from the ignition coil on cylinder 3.
3. Remove the Ignition Coil: Use a socket to remove the bolt securing the ignition coil, then gently pull it out.
4. Remove Spark Plug: Use a spark plug socket to unscrew and remove the spark plug from cylinder 3.
5. Inspect Spark Plug: Check for signs of wear or fouling. Replace if necessary with a new spark plug that meets OEM specifications.
6. Reinstall Spark Plug and Coil: Reverse the removal steps to reinstall the spark plug and ignition coil, ensuring proper torque (typically 15-20 Nm for spark plugs).

3. Inspect and Replace Fuel Injector

1. Remove Fuel Rail (if necessary): If the injector is obstructed, disconnect the fuel supply line and remove the fuel rail.
2. Remove Fuel Injector: Carefully pull the injector out of its socket, ensuring not to damage the surrounding components.
3. Inspect Injector: Check for blockages or damage; clean or replace with a new OEM injector as needed.
4. Reinstall Fuel Injector and Rail: If removed, reinstall the fuel rail and reconnect the fuel supply line, ensuring all connections are tight.

4. Perform Compression Test (if needed)

1. Remove Spark Plug from Cylinder 3: As previously described.
2. Insert Compression Tester: Screw the compression tester into the spark plug hole.
3. Crank the Engine: Have an assistant crank the engine for about 5 seconds while observing the pressure gauge.
4. Record the Pressure: Compare the reading to the vehicle's specifications (typically between 140-200 psi).
5. Reinstall Spark Plug: Replace the spark plug after testing.