what does it mean when my BMW 3 Series E90/E91 (2005-2012) has a P0302 code?

Solution

1. Preparation

• Gather necessary tools and replacement parts.
• Disconnect the negative battery cable to ensure safety.
• Allow the engine to cool down before beginning work.

2. Inspect and Replace Spark Plug

• Remove the ignition coil for cylinder 2:
  • Unplug the electrical connector.
  • Remove the retaining bolts using a socket set.
• Remove the spark plug using a spark plug socket.
• Inspect the spark plug for wear or fouling; replace it if necessary with the specified part for your model.
• Reinstall the spark plug and ignition coil, ensuring all connections are secure.

3. Inspect and Replace Ignition Coil

• If the spark plug is in good condition, test the ignition coil:
  • Swap the ignition coil from cylinder 2 with another cylinder.
  • Clear the P0302 code and monitor for a new misfire code.
• If a misfire code moves to the other cylinder, replace the ignition coil with a new one.
• Reinstall any components removed during the process.

4. Check Fuel Injector

• Disconnect the fuel injector connector for cylinder 2.
• Perform a resistance test on the injector using a multimeter; compare with specifications.
• If the injector is faulty, replace it with a new one. Ensure proper seating and reconnect the electrical connector.

5. Compression Test

• If misfires persist after replacing the spark plug and ignition coil, conduct a compression test:
  • Remove all spark plugs for easy access.
  • Insert the compression gauge into cylinder 2 and crank the engine.
  • Compare the readings to OEM specifications; if low, further investigation into the engine internals is necessary.