how to fix P0303 misfire code in BMW X3 G01 (2018-2024)

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, multimeter, compression tester, fuel injector cleaner.
• Disconnect the negative battery terminal to prevent electrical shock.
• Allow the engine to cool down before starting any work.

2. Inspect and Replace Spark Plug

• Remove the engine cover if applicable.
• Use a spark plug socket to remove the spark plug from cylinder 3.
• Inspect the spark plug for signs of wear or fouling. Replace if necessary.
  • Torque for new spark plug: 22 lb-ft (30 Nm).
• Reinstall the spark plug and reattach the engine cover.

3. Test and Replace Ignition Coil

• Disconnect the electrical connector from the ignition coil on cylinder 3.
• Remove the ignition coil using a socket wrench.
• Measure the resistance of the coil using a multimeter. The resistance should be within the manufacturer specifications (typically around 0.5-1.5 ohms).
• If the ignition coil is faulty, replace it with a new one.
• Reinstall the ignition coil and reconnect the electrical connector.

4. Inspect and Clean Fuel Injector

• Disconnect the electrical connector and fuel line from the fuel injector for cylinder 3.
• Remove the fuel injector using the appropriate tool or socket.
• Clean the injector with a fuel injector cleaner or replace it if it’s clogged or malfunctioning.
• Reinstall the fuel injector and reconnect the electrical connector and fuel line.

5. Compression Test

• Remove the spark plug from cylinder 3.
• Insert the compression tester into the spark plug hole.
• Crank the engine to get a reading. The compression should be within the manufacturer’s specifications (generally around 130-200 psi).
• If compression is low, further internal engine diagnostics may be necessary (valve issues, piston rings).