my BMW 3 Series E90/E91 (2005-2012) has a check engine light with code P0301 what does it mean

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool before beginning work.

2. Inspect and Replace Spark Plug

• Remove the ignition coil for cylinder 1 by unscrewing the bolts and gently pulling it out.
• Remove the spark plug using a spark plug socket and ratchet.
• Inspect the spark plug for wear or carbon buildup. Replace if necessary.
• Torque the new spark plug to the manufacturer's specification (typically around 15-20 lb-ft).
• Reinstall the ignition coil.

3. Check and Replace Ignition Coil (if necessary)

• If the spark plug is in good condition but the misfire persists, test the ignition coil with a multimeter for resistance.
• If out of specification, replace the ignition coil with a new one.
• Ensure it is properly seated and secured.

4. Inspect and Clean Fuel Injector

• Disconnect the fuel injector connector for cylinder 1.
• Remove the fuel injector from the rail.
• Clean the injector with a specialized cleaner or replace it if clogged or faulty.
• Reinstall the fuel injector and reconnect the electrical connector.

5. Perform Compression Test

• If the misfire persists after replacing the spark plug, ignition coil, and fuel injector, perform a compression test.
• Remove the spark plug and insert the compression gauge.
• Crank the engine and record the pressure. Compare to specifications (typically around 130-150 psi).
• If compression is low, further engine diagnostics may be needed.