why does my BMW X3 F25 (2011-2018) have a check engine light for P0304?

Solution

1. Preparation

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

2. Inspect and Replace Spark Plug

• Tools Required: Spark plug socket, torque wrench, ratchet.
• Remove the ignition coil on cylinder 4.
• Extract the spark plug using the spark plug socket.
• Inspect the spark plug for wear or damage; replace if necessary.
• Torque the new spark plug to the manufacturer's specifications (usually around 18-25 Nm).

3. Inspect and Replace Ignition Coil

• Remove the ignition coil from cylinder 4.
• Check for cracks or damage; replace if needed.
• Ensure the new ignition coil is seated properly and connected securely.

4. Test Fuel Injector

• Tools Required: Multimeter, fuel injector tester (optional).
• Disconnect the fuel injector connector for cylinder 4.
• Test the injector resistance with a multimeter (check specifications; typically around 12-16 ohms).
• If faulty, replace the fuel injector.

5. Check for Vacuum Leaks

• Inspect all hoses and gaskets around the intake manifold.
• Use a smoke machine or carburetor cleaner to check for leaks.
• Repair any leaks found by replacing damaged hoses or gaskets.

6. Compression Test

• Tools Required: Compression tester.
• Remove the spark plug for cylinder 4 and insert the compression tester.
• Crank the engine and note the compression reading; it should be within manufacturer specifications (typically 130-190 psi).
• If low, further diagnosis may be required for internal engine issues.