how to diagnose a P0302 misfire code on BMW 3 Series F30/F31 (2012-2019)?

Solution

1. Preparation

• Gather tools and parts. Ensure the vehicle is parked on a level surface and the engine is cool.
• Tools Required:
  • OBD-II scanner
  • Socket set
  • Torque wrench
  • Compression tester
  • Multimeter
  • Fuel injector cleaning kit (if necessary)

2. Replace Spark Plug

• Sub-steps:
  1. Remove the engine cover if applicable.
  2. Disconnect the ignition coil connector for cylinder 2.
  3. Remove the ignition coil using a socket.
  4. Unscrew the spark plug using a spark plug socket.
  5. Install a new spark plug, ensuring it is gapped correctly to manufacturer specifications.
  6. Reinstall the ignition coil and reconnect the wiring harness.
• Safety Warning: Ensure the engine is cold before working on the spark plugs to avoid burns.

3. Inspect and Replace Ignition Coil

• Sub-steps:
  1. Replace the ignition coil for cylinder 2 if visual inspection shows damage or if misfire persists after spark plug replacement.
  2. Connect the new ignition coil and torque it to manufacturer specifications.
  3. Reconnect the electrical connector.

4. Test Fuel Injector

• Sub-steps:
  1. Disconnect the fuel injector connector for cylinder 2.
  2. Use a multimeter to check for proper voltage at the connector.
  3. If no voltage is detected, trace wiring back to the engine control unit (ECU).
  4. If voltage is present, use a fuel injector cleaning kit to clean or replace the injector as necessary.

5. Perform Compression Test

• Sub-steps:
  1. Remove the spark plug for cylinder 2.
  2. Insert the compression tester into the spark plug hole.
  3. Crank the engine a few times and record the compression reading.
  4. Compare the reading to the manufacturer’s specifications to determine if the cylinder is healthy.